diff --git a/CotEditor/Sources/AddRemoveButton.swift b/CotEditor/Sources/AddRemoveButton.swift
index 79b577eb2..c155c0f76 100644
--- a/CotEditor/Sources/AddRemoveButton.swift
+++ b/CotEditor/Sources/AddRemoveButton.swift
@@ -25,13 +25,7 @@
 
 import SwiftUI
 
-protocol EmptyInitializable {
-    
-    init()
-}
-
-
-struct AddRemoveButton<Item: Identifiable & EmptyInitializable>: View {
+struct AddRemoveButton<Item: Identifiable>: View {
     
     @Binding private var items: [Item]
     @Binding private var selection: Set<Item.ID>
@@ -39,6 +33,8 @@ struct AddRemoveButton<Item: Identifiable & EmptyInitializable>: View {
     private var focus: FocusState<Item.ID?>.Binding?
     @State private var added: Item.ID?
     
+    private var newItem: () -> Item
+    
     
     /// Creates a  segmented add/remove control.
     ///
@@ -46,11 +42,13 @@ struct AddRemoveButton<Item: Identifiable & EmptyInitializable>: View {
     ///   - items: The identifiable data array where adding/removing items.
     ///   - selection: A binding to a set that identifies selected items IDs.
     ///   - focus: A binding to the focus state in the window.
-    init(_ items: Binding<[Item]>, selection: Binding<Set<Item.ID>>, focus: FocusState<Item.ID?>.Binding? = nil) {
+    ///   - newItem: A closure to return an item for when adding a new item from the button.
+    init(_ items: Binding<[Item]>, selection: Binding<Set<Item.ID>>, focus: FocusState<Item.ID?>.Binding? = nil, newItem: @escaping () -> Item) {
         
         self._items = items
         self._selection = selection
         self.focus = focus
+        self.newItem = newItem
     }
     
     
@@ -58,7 +56,7 @@ struct AddRemoveButton<Item: Identifiable & EmptyInitializable>: View {
         
         ControlGroup {
             Button(String(localized: "Add", table: "AddRemoveButton", comment: "button label"), systemImage: "plus") {
-                let item = Item()
+                let item = self.newItem()
                 let index = self.items.lastIndex { self.selection.contains($0.id) } ?? self.items.endIndex - 1
                 
                 self.selection.removeAll()
diff --git a/CotEditor/Sources/SyntaxCompletionEditView.swift b/CotEditor/Sources/SyntaxCompletionEditView.swift
index 66cf96011..8c4d36a4e 100644
--- a/CotEditor/Sources/SyntaxCompletionEditView.swift
+++ b/CotEditor/Sources/SyntaxCompletionEditView.swift
@@ -59,7 +59,7 @@ struct SyntaxCompletionEditView: View {
             .border(Color(nsColor: .gridColor))
             
             HStack {
-                AddRemoveButton($items, selection: $selection, focus: $focusedField)
+                AddRemoveButton($items, selection: $selection, focus: $focusedField, newItem: Item.init)
                 Spacer()
                 HelpButton(anchor: "syntax_highlight_settings")
             }
diff --git a/CotEditor/Sources/SyntaxFileMappingEditView.swift b/CotEditor/Sources/SyntaxFileMappingEditView.swift
index 863273f41..f7408fe74 100644
--- a/CotEditor/Sources/SyntaxFileMappingEditView.swift
+++ b/CotEditor/Sources/SyntaxFileMappingEditView.swift
@@ -112,7 +112,7 @@ struct SyntaxFileMappingEditView: View {
                 .alternatingRowBackgrounds()
                 .border(Color(nsColor: .gridColor))
                 
-                AddRemoveButton($items, selection: $selection, focus: $focusedField)
+                AddRemoveButton($items, selection: $selection, focus: $focusedField, newItem: Item.init)
             }.accessibilityElement(children: .contain)
         }
     }
diff --git a/CotEditor/Sources/SyntaxHighlightEditView.swift b/CotEditor/Sources/SyntaxHighlightEditView.swift
index c0fa8fd5b..b25ff4e5e 100644
--- a/CotEditor/Sources/SyntaxHighlightEditView.swift
+++ b/CotEditor/Sources/SyntaxHighlightEditView.swift
@@ -104,7 +104,7 @@ struct SyntaxHighlightEditView: View {
             .border(Color(nsColor: .gridColor))
             
             HStack {
-                AddRemoveButton($items, selection: $selection, focus: $focusedField)
+                AddRemoveButton($items, selection: $selection, focus: $focusedField, newItem: Item.init)
                 Spacer()
                 HelpButton(anchor: self.helpAnchor)
             }
diff --git a/CotEditor/Sources/SyntaxObject.swift b/CotEditor/Sources/SyntaxObject.swift
index e91723035..f2ae8c49b 100644
--- a/CotEditor/Sources/SyntaxObject.swift
+++ b/CotEditor/Sources/SyntaxObject.swift
@@ -77,7 +77,7 @@ import Observation
 }
 
 
-struct SyntaxObjectHighlight: Identifiable, EmptyInitializable {
+struct SyntaxObjectHighlight: Identifiable {
     
     let id = UUID()
     
@@ -89,7 +89,7 @@ struct SyntaxObjectHighlight: Identifiable, EmptyInitializable {
 }
 
 
-struct SyntaxObjectOutline: Identifiable, EmptyInitializable {
+struct SyntaxObjectOutline: Identifiable {
     
     let id = UUID()
     
@@ -103,7 +103,7 @@ struct SyntaxObjectOutline: Identifiable, EmptyInitializable {
 }
 
 
-struct SyntaxObjectKeyString: Identifiable, EmptyInitializable {
+struct SyntaxObjectKeyString: Identifiable {
     
     let id = UUID()
     
diff --git a/CotEditor/Sources/SyntaxOutlineEditView.swift b/CotEditor/Sources/SyntaxOutlineEditView.swift
index fedf288ad..c5602e576 100644
--- a/CotEditor/Sources/SyntaxOutlineEditView.swift
+++ b/CotEditor/Sources/SyntaxOutlineEditView.swift
@@ -64,7 +64,7 @@ struct SyntaxOutlineEditView: View {
             .tableStyle(.bordered)
             .border(Color(nsColor: .gridColor))
             
-            AddRemoveButton($items, selection: $selection, focus: $focusedField)
+            AddRemoveButton($items, selection: $selection, focus: $focusedField, newItem: Item.init)
                 .padding(.bottom, 8)
             
             if self.selection.count > 1 {