fix #52491

src/vs/workbench/common/editor.ts

@@ -625,10 +625,6 @@ export class SideBySideEditorInput extends EditorInput {
 		return this.description;
 	}
 
-	public supportsSplitEditor(): boolean {
-		return false;
-	}
-
 	public matches(otherInput: any): boolean {
 		if (super.matches(otherInput) === true) {
 			return true;

src/vs/workbench/services/preferences/common/preferencesEditorInput.ts

@@ -23,10 +23,6 @@ export class PreferencesEditorInput extends SideBySideEditorInput {
 		return PreferencesEditorInput.ID;
 	}
 
-	public supportsSplitEditor(): boolean {
-		return true;
-	}
-
 	public getTitle(verbosity: Verbosity): string {
 		return this.master.getTitle(verbosity);
 	}