Use new hint

[memeplex]

Soon you will be able to use linuxmint/cinnamon#7681. This is a more dynamic solution (the wm shows/hides decorations wrt the current window state) and also more robust (since you're hinting the wm instead of overriding its behavior). It's easy to hack a script using xprop and bind it to some key, but nevertheless it could be nice to keep an applet in the panel like yours. Maybe you would want to update your solution.

[memeplex]

Btw I'm already providing a more global solution based on the hint (https://github.com/memeplex/maximal) but yours is complementary since it targets only selected windows.