I should clarify my earlier posts.
To start at the beginning, on Mac there are three possible sources of keyboard shortcuts:
- macOS itself
- compiled menus in SketchUp
- SketchUp user preferences
The first two kinds are preempted by macOS or by the app’s compiled menu system. They use command key-chords (i.e. simultaneous presses of one or more other keys along with the command key) as shortcuts. These key-chords fire commands immediately without even passing the keypresses through to the SketchUp user Preferences shortcut system.
The menus use key-chords that in many cases are conventional across all normal macOS apps, such as Cmd-S=> File/Save and Cmd-X => Edit/Cut. The shortcuts are shown next to each menu item when you open a menu. Menu shortcuts are compiled into the app and can’t be modified without recompiling, which an end-user can’t do.
The SketchUp user Preferences system loads a separate default suite of user-editable shortcuts and target actions. These are all available for modification by the user, and you can define new shortcuts for any target action listed in the Preferences dialog. The target list includes the ones already assigned via menu item shortcuts, which allows you to create personal aliases for those items. But to avoid confusion about why you can’t change them, Preferences does not display the macOS or menu command key-chords and does not allow you to assign a command key-chord via the dialog.
These behaviors can be confusing to users coming from Windows, where the menu shortcuts can be reassigned via SketchUp’s preferences.