Hey Nutti, big thanks for making this addon,
when I try to use the UV pack extension, at first it appears to work in the UV window, but on closer inspection, although the verts are properly welding between the two islands being stacked, one of the islands ( in this case those at the top) has had each of its faces made into a separate island, and those faces/islands are rotated (seemingly 90 degr

Implement the ability to choose various animation playback types such as "loop" or "boomerang". This would be implemented in the handle_animation function.

This is a very simple feature to implement (development time <1 hour).