This seems like a decent start, but there are unfortunately quite a few issues preventing it from being useful:
- there's no metadata exported alongside the spritesheet that tells you how to retrieve a specific sprite
- there's no way to remove a sprite once added
- the sprites in the exported file don't match the scale of the original files, and linear interpolation is applied which will generally make pixel-art look worse
- the preview only updates when you save
- it always saves to a single file path instead of prompting where to save, overwriting any existing file without confirmation