How can I assign an arrow key (like the left arrow) to be the keyboard shortcut of a menu item?
Even if I have to catch the shortcut myself, how do I even display it in the menubar? Adding a high ascii “?” emoji into the menuItem displays as [?]
Xojo understands (and maps) a lot of these shortcuts.
For instance, put “leftarrow” in the “key” field of the menu item and you get a ? that works. Tab and such are also available.
That’s a shame
The documentation mentions F1-F15; my keyboard goes up to F16, that useless-for-menu item-shortcut key 
and mine stop at F12 
Hmm
If I ever make an app for you, I’ll be kidding by assigning F13 to F16 shortcuts to my menu items 
The left part of my keyboard ends with F13; then, above the delete and help block, I have F14 thru F16.
My MacBook Pro ends with F12, like your. I guess, with all these combinations, that higher function keys are more suitable for user’s customisations.
Ah. It’s RTFM! 
That works. Thanks!