I like the software a lot so far but I do have a few issues with it.
1. There's currently no way to zoom on the output or render preview, which makes it extremely hard to get a good look at the animations when dealing with low resolutions.
2. There's options for handling spread (0-180) but I haven't been able to find anything to make sure the spread is completely symmetrical, for higher resolutions this isn't really an issue but for low resolutions it means having to edit the sprite sheets by hand after making it, which can be quite a bit of work.
3. Changing the output scale doesn't affect the render preview. Great quality of life improvement to be able to see what the scaled output will look like without having to save it to a .png sprite sheet first.
Aside from those 3 things and a Undo/Redo button I don't feel like anything is missing at least for now, great job making BlastFX!