In the online version everything works just fine, but in the win-version there are some oddities...
First - the same button behaves differently, which is wrong in itself.
Second - after clicking on "Save" the program doesn't confirm that it saved the project in any way.
Possible solutions.
Add a small hint message "Saved!"
Make two save buttons. There's plenty of space for one more icon, no problem with that yet at all.
Leave only saving as a zip file. To be honest, I don't understand why you need two saving formats at once, considering that the program opens and works perfectly well with zip files.
A wish for the future: Autosave and save button should have three slots. In other words, do not instantly overwrite the previous version, but save the second file. Then the third. And only then overwrite the first.
In the online version everything works just fine, but in the win-version there are some oddities... First - the same button behaves differently, which is wrong in itself. Second - after clicking on "Save" the program doesn't confirm that it saved the project in any way.
Possible solutions.
A wish for the future: Autosave and save button should have three slots. In other words, do not instantly overwrite the previous version, but save the second file. Then the third. And only then overwrite the first.