diff --git a/CHANGELOG.md b/CHANGELOG.md
index e04e1ca97..a8c4fda2c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
 ### New Features
 
 - Support __macOS 15 Sequoia__.
+- Accept folders to open and navigate the content in the new directory navigation sidebar.
 - [AppStore ver.] Now the user can donate to the CotEditor project via in-app purchase in the new Donate settings pane.
 - Add new “Select Enclosing Symbols” and “Split Selection by Lines” commands to the Edit > Select menu.
 - Support the alpha channel for the current line in theme settings.
diff --git a/CotEditor/CotEditor.help/Contents/Resources/en.lproj/pgs/whats_new_in_4.8.html b/CotEditor/CotEditor.help/Contents/Resources/en.lproj/pgs/whats_new_in_4.8.html
index c76b32c39..31966f5c2 100644
--- a/CotEditor/CotEditor.help/Contents/Resources/en.lproj/pgs/whats_new_in_4.8.html
+++ b/CotEditor/CotEditor.help/Contents/Resources/en.lproj/pgs/whats_new_in_4.8.html
@@ -10,7 +10,6 @@
 </head>
 
 <body>
-<a name="whats_new"></a>
 
 <h1>What’s new in CotEditor 4.8?</h1>
 
@@ -28,6 +27,7 @@
 <ul>
 	<li><a href="releasenotes.html">Release notes</a></li>
 	<li><a href="whats_new_in_4.7.html">What’s new in CotEditor 4.7?</a></li>
+	<li><a href="whats_new_in_5.0.html">What’s new in CotEditor 5.0?</a></li>
 </ul>
 </section>
 
diff --git a/CotEditor/CotEditor.help/Contents/Resources/en.lproj/pgs/whats_new_in_5.0.html b/CotEditor/CotEditor.help/Contents/Resources/en.lproj/pgs/whats_new_in_5.0.html
new file mode 100644
index 000000000..adf9fefae
--- /dev/null
+++ b/CotEditor/CotEditor.help/Contents/Resources/en.lproj/pgs/whats_new_in_5.0.html
@@ -0,0 +1,38 @@
+<html lang="en">
+
+<head>
+	<meta charset="UTF-8"/>
+	<meta name="keywords" content="what's new, highlights, release"/>
+	<link rel="stylesheet" href="../../Shared/sty/standard.css"/>
+	<script defer src="../../Shared/js/toc.js"></script>
+	
+	<title>What’s new in CotEditor 5.0?</title>
+</head>
+
+<body>
+<a name="whats_new"></a>
+
+<h1>What’s new in CotEditor 5.0?</h1>
+
+<dl>
+	<dt>macOS 15 Sequoia Support</dt>
+	<dd>Work perfectly with new macOS 15.</dd>
+	
+	<dt>Folder Navigation</dt>
+	<dd>Open a folder in CotEditor to navigate its content in the new sidebar.</dd>
+	
+	<dt>Donation</dt>
+	<dd>Support the CotEditor project by offering coffee to the developer.</dd>
+</dl>
+
+
+<section id="cf">
+<h2>See also</h2>
+<ul>
+	<li><a href="releasenotes.html">Release notes</a></li>
+	<li><a href="whats_new_in_4.8.html">What’s new in CotEditor 4.8?</a></li>
+</ul>
+</section>
+
+</body>
+</html>
diff --git a/CotEditor/CotEditor.help/Contents/Resources/en.lproj/toc.html b/CotEditor/CotEditor.help/Contents/Resources/en.lproj/toc.html
index a1ee921df..4ad1241fc 100644
--- a/CotEditor/CotEditor.help/Contents/Resources/en.lproj/toc.html
+++ b/CotEditor/CotEditor.help/Contents/Resources/en.lproj/toc.html
@@ -134,6 +134,7 @@
 			<li><details>
 				<summary>What’s New</summary>
 				<ul>
+					<li><a href="pgs/whats_new_in_5.0.html">What’s new in CotEditor 5.0?</a></li>
 					<li><a href="pgs/whats_new_in_4.8.html">What’s new in CotEditor 4.8?</a></li>
 					<li><a href="pgs/whats_new_in_4.7.html">What’s new in CotEditor 4.7?</a></li>
 					<li><a href="pgs/whats_new_in_4.6.html">What’s new in CotEditor 4.6?</a></li>
diff --git a/CotEditor/CotEditor.help/Contents/Resources/ja.lproj/pgs/whats_new_in_4.8.html b/CotEditor/CotEditor.help/Contents/Resources/ja.lproj/pgs/whats_new_in_4.8.html
index a8cba0939..a1ade6bb9 100644
--- a/CotEditor/CotEditor.help/Contents/Resources/ja.lproj/pgs/whats_new_in_4.8.html
+++ b/CotEditor/CotEditor.help/Contents/Resources/ja.lproj/pgs/whats_new_in_4.8.html
@@ -10,7 +10,6 @@
 </head>
 
 <body>
-<a name="whats_new"></a>
 
 <h1>CotEditor 4.8の新機能</h1>
 
@@ -27,8 +26,8 @@
 <h2>関連項目</h2>
 <ul>
 	<li><a href="releasenotes.html">リリースノート</a></li>
-	<li><a href="whats_new_in_4.6.html">CotEditor 4.6の新機能</a></li>
-	<li><a href="whats_new_in_4.6.html">CotEditor 4.8の新機能</a></li>
+	<li><a href="whats_new_in_4.7.html">CotEditor 4.7の新機能</a></li>
+	<li><a href="whats_new_in_5.0.html">CotEditor 5.0の新機能</a></li>
 </ul>
 </section>
 
diff --git a/CotEditor/CotEditor.help/Contents/Resources/ja.lproj/pgs/whats_new_in_5.0.html b/CotEditor/CotEditor.help/Contents/Resources/ja.lproj/pgs/whats_new_in_5.0.html
new file mode 100644
index 000000000..216e70149
--- /dev/null
+++ b/CotEditor/CotEditor.help/Contents/Resources/ja.lproj/pgs/whats_new_in_5.0.html
@@ -0,0 +1,38 @@
+<html lang="ja">
+
+<head>
+	<meta charset="UTF-8"/>
+	<meta name="keywords" content="what's new, リリース, 新機能"/>
+	<link rel="stylesheet" href="../../Shared/sty/standard.css"/>
+	<script defer src="../../Shared/js/toc.js"></script>
+	
+	<title>CotEditor 5.0の新機能</title>
+</head>
+
+<body>
+<a name="whats_new"></a>
+
+<h1>CotEditor 5.0の新機能</h1>
+
+<dl>
+	<dt>macOS 15 Sequoiaサポート</dt>
+	<dd>新しいmacOSを完全にサポートしています。</dd>
+	
+	<dt>フォルダナビゲーション</dt>
+	<dd>フォルダをCotEditorで開いて新しいサイドバーで内容をナビゲート。</dd>
+	
+	<dt>寄付</dt>
+	<dd>開発者にコーヒーを送ってCotEditorプロジェクトをサポート。</dd>
+</dl>
+
+
+<section id="cf">
+<h2>関連項目</h2>
+<ul>
+	<li><a href="releasenotes.html">リリースノート</a></li>
+	<li><a href="whats_new_in_4.6.html">CotEditor 4.8の新機能</a></li>
+</ul>
+</section>
+
+</body>
+</html>
diff --git a/CotEditor/CotEditor.help/Contents/Resources/ja.lproj/toc.html b/CotEditor/CotEditor.help/Contents/Resources/ja.lproj/toc.html
index df90e5327..0666f572f 100644
--- a/CotEditor/CotEditor.help/Contents/Resources/ja.lproj/toc.html
+++ b/CotEditor/CotEditor.help/Contents/Resources/ja.lproj/toc.html
@@ -134,6 +134,7 @@
 			<li><details>
 				<summary>新機能</summary>
 				<ul>
+					<li><a href="pgs/whats_new_in_5.0.html">CotEditor 5.0の新機能</a></li>
 					<li><a href="pgs/whats_new_in_4.8.html">CotEditor 4.8の新機能</a></li>
 					<li><a href="pgs/whats_new_in_4.7.html">CotEditor 4.7の新機能</a></li>
 					<li><a href="pgs/whats_new_in_4.6.html">CotEditor 4.6の新機能</a></li>
diff --git a/CotEditor/Localizables/WhatsNew.xcstrings b/CotEditor/Localizables/WhatsNew.xcstrings
index 55d8cb93a..5a306ba3b 100644
--- a/CotEditor/Localizables/WhatsNew.xcstrings
+++ b/CotEditor/Localizables/WhatsNew.xcstrings
@@ -179,6 +179,64 @@
         }
       }
     },
+    "NewFeature.folderNavigation.description" : {
+      "extractionState" : "extracted_with_value",
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Einen Ordner in CotEditor öffnen, um durch seinen Inhalt in der neuen Seitenleiste zu navigieren."
+          }
+        },
+        "en" : {
+          "stringUnit" : {
+            "state" : "new",
+            "value" : "Open a folder in CotEditor to navigate its content in the new sidebar."
+          }
+        },
+        "en-GB" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Open a folder in CotEditor to navigate its content in the new sidebar."
+          }
+        },
+        "ja" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "フォルダをCotEditorで開いて新しいサイドバーで内容をナビゲート。"
+          }
+        }
+      }
+    },
+    "NewFeature.folderNavigation.label" : {
+      "extractionState" : "extracted_with_value",
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Ordnernavigation"
+          }
+        },
+        "en" : {
+          "stringUnit" : {
+            "state" : "new",
+            "value" : "Folder Navigation"
+          }
+        },
+        "en-GB" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Folder Navigation"
+          }
+        },
+        "ja" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "フォルダナビゲーション"
+          }
+        }
+      }
+    },
     "NewFeature.macOSSupport.description" : {
       "extractionState" : "extracted_with_value",
       "localizations" : {
diff --git a/CotEditor/Sources/WhatsNewView.swift b/CotEditor/Sources/WhatsNewView.swift
index bbc877587..4deacf1ce 100644
--- a/CotEditor/Sources/WhatsNewView.swift
+++ b/CotEditor/Sources/WhatsNewView.swift
@@ -127,6 +127,7 @@ private enum NewFeature: CaseIterable {
     static let version = "5.0"
     
     case macOSSupport
+    case folderNavigation
     case donation
     
     
@@ -135,6 +136,8 @@ private enum NewFeature: CaseIterable {
         switch self {
             case .macOSSupport:
                 Image(systemName: "sparkles")
+            case .folderNavigation:
+                Image(systemName: "folder")
             case .donation:
                 Image(.bagCoffee)
         }
@@ -147,6 +150,9 @@ private enum NewFeature: CaseIterable {
             case .macOSSupport:
                 String(localized: "NewFeature.macOSSupport.label",
                        defaultValue: "macOS 15 Sequoia Support", table: "WhatsNew")
+            case .folderNavigation:
+                String(localized: "NewFeature.folderNavigation.label",
+                       defaultValue: "Folder Navigation", table: "WhatsNew")
             case .donation:
                 String(localized: "NewFeature.donation.label",
                        defaultValue: "Donation", table: "WhatsNew")
@@ -160,6 +166,9 @@ private enum NewFeature: CaseIterable {
             case .macOSSupport:
                 String(localized: "NewFeature.macOSSupport.description",
                        defaultValue: "Work perfectly with new macOS 15.", table: "WhatsNew")
+            case .folderNavigation:
+                String(localized: "NewFeature.folderNavigation.description",
+                       defaultValue: "Open a folder in CotEditor to navigate its content in the new sidebar.", table: "WhatsNew")
             case .donation:
                 String(localized: "NewFeature.donation.description",
                        defaultValue: "Support the CotEditor project by offering coffee to the developer.", table: "WhatsNew")
