When I've created an album, and I made it a personal album (so I've placed it @ My Gallery), I can't edit the ' Album category'... When I come on modifyalb.php, there is no such field... But when I create a album not at My Gallery, I can select in which category I want to place it... Is there a way to make I can put EVERY album into a category, after they've been created as a my gallery album?
No, can't be done, without messing with the database, not recommended.