Here is a feature request.
In the actual Windows Explorer, whenever you go to Properties for a file, you get a Properties Window. This window has controls which look like Labels (Static), but are actually read-only Text Boxes with no borders (Edit). So you can click on these, select text, copy it to the clipboard, etc.
Meanwhile, in Mp3tag, the properties window only has Labels (Static). You can not copy text out of these without using a special program.
I'd request that the Labels in the properties window be replaced with Read-Only Text Boxes with hidden borders, so they look just like the labels, but instead can have text copied out.