src/vs/workbench/contrib/mergeEditor/browser/commands/commands.ts/SetMixedLayout/constructor
class SetMixedLayout:	constructor() {
		super({
			id: 'merge.mixedLayout',
			title: localize('layout.mixed', "Mixed Layout"),
			toggled: ContextKeyExpr.equals(ctxMergeEditorLayout.key, 'mixed'),
			menu: [{
				id: MenuId.EditorTitle,
				when: ctxIsMergeEditor,
				group: '1_merge',
				order: 9,
			}]
		});
	}