After a user request to allow adding empty frames to a sprite sheet, I added an old version of G.A.S. to download, next to the current version.

The old version allows you to add empty frames. To do so, you need to:

1) import frames

2) deselect "auto-adjust to include all frames"

3) set the columns and rows to the desired values

4) increase the last frame value to include the empty frames

Next you can export the sprite sheet and the empty area will be included!

Thanks for reading!