I've found that using the backpack is significantly difficult, being only able to store sprites and scripts, and not costumes. When in a “backpack recovery” project i made in 2.0, continuously attempting to open up the backpack and store costumes causes the 3.0 editor to crash. Later projects won't crash, but the backpack refuses to open when in costumes. 2.0 backpack opened up no matter what. Is the “not able to store costumes” current feature part of the editor, or is it a bug, which needs fixing?

I've just copied a costume to the backpack. My backpack was otherwise empty. I deleted the project and created a new one and the costume was in the backpack.

My browser / operating system: Windows NT 10.0, Firefox 64.0, Flash 32.0 (release 0)