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

Gonna save me tons of time making future sprite sheets, Thanks for the useful tool!