To give it the Windows XP look, right-click the taskbar and choose "Properties." In the RetroBar Properties window, click the dropdown icon next to Theme and select "Windows XP Blue ...

Back in Windows XP, apps on the taskbar would still be labeled and each instance of an app would be shown separately until ...

At first, you need to open the Windows ... on the Taskbar and select the Taskbar settings option. Following that, you need to toggle the corresponding button to show the Pen menu icon.