On macOS, Undo is Cmd+Shift+Z, not Cmd+Y. The F1-F12 keys are a pain to use, as they are, by default, mapped to stuff like changing the brightness. Zoom In reacts to both Cmd+ and Cmd=. Right now, it seems to react to neither. Cmd+Backspace deletes from the cursor to the beginning of the line, and Option+Backspace deletes the previous word, but I don't see a function like that in Geany.

These issues should be addressed by

https://github.com/geany/geany/pull/1395

and

https://github.com/geany/geany/pull/1633

https://github.com/geany/geany/pull/1395 is waiting until someone creates better default keybindings for Mac (you?) and I'm not sure what's blocking https://github.com/geany/geany/pull/1633

Preferences is usually under the Geany menu and has the shortcut Cmd+Comma (but it is usually automatic). There is a way to set the menu item to function as the Preferences menu, but I don't know it off hand.

I did this originally and I would prefer it this way but someone complained that they don't like when each platform behaves differently so I reverted it back. Is easy to do tough if there's some agreement we want this.

Mac has a built-in fullscreen mode which seems to function like Geany's, so the menu option can be disabled.

Yeah, this one could probably be done but it's just a cosmetic thing and not sure if worth cluttering the Geany code with platform-specific stuff.