I accidentally deleted a costume that I don't feel like redrawing. How can I get it back?
Did you save recently before the incident?
Save your project
Then try using open - recover to see if you can get a version that contains your costume
If so - export your costume and the re-import it into current project
File > Undelete Sprites
That's only for deleted sprites, not costumes. I had a similar idea, but I tested it with deleting a costume, and it didn't work.
Oh, costumes. My bad, I confused the two.