Hi. I just tried it with WordPress Version 3.5.1, and it works! Thank you. I just have to shorten all my theme zip-file names to fit the menu widget.
Suggestion: how about adding to the plugin an admin ability to edit theme names from the dashboard, so they do fit the widget menu, i.e., so we could adjust theme name's length depending on the width of our sidebar. Would save re-doing and re-uploading the zip files.
This is brilliant, thank you!