src/vs/workbench/browser/parts/editor/editorGroupView.ts/EditorGroupView/isLocked
class EditorGroupView:	get isLocked(): boolean {
		if (this.accessor.groups.length === 1) {
			// Special case: if only 1 group is opened, never report it as locked
			// to ensure editors can always open in the "default" editor group
			return false;
		}

		return this.model.isLocked;
	}