I think it would be useful to be able to open multiple instances of MP3Tag at the same time. I often open one instance with my whole MP3 collection which takes a long time, as you can imagine. As I'm going through working on tags, I sometimes need to open another instance on a folder I had previous worked on so I can compare information, but it's not possible to do so. Sometimes I forget and open MP3Tag on the second folder anyway, and then I have to re-open it (taking a long time) on the larger collection of MP3s.
Do you think it would be possible to include this feature in an upcoming release?