Hi!
When I making a block and I changed its category and start editing
my block I have a variables category:
despite I change the category. Why it happening?
Try clicking "apply".
Yes, this changed to right category. But itself fact, it say to fix this.
This bug can mislead 
I think the question about the category changing is the least of the issues with not clicking Apply. Some software (most notably Google Docs) have eliminated the issue with instant-save, but that has its own problems; I want to be in charge of whether or not to commit a change I'm making.
Maybe a setting to enable auto-save? I have an auto-save block the runs JS to save the project every 60 seconds (or however much you want). It's in this project: Snap! 6.9.2 Build Your Own Blocks
Auto-saving the whole project is a slightly different issue from auto-applying changes in the Block Editor.
But anyway, the trouble with options is that checking them takes time, slowing down Snap!.
yup it is
It wasn't even a bug.