Place the current selection on the Clipboard and delete it. Standard macOS key command since the beginning.
‘Cut’ is available on the X-Touch and MCU by pressing ‘CMD+F1’
Cut, copy and paste in the Logic Pro Audio Track Editor — Apple Support
In Logic Pro, select the region or region segment with the Marquee Tool, then choose Edit > Cut (or press Delete).
or press ⌘X
NB when the Key Commands window indicates that there are “assignments” you can double-click on a listed assignment to open the ‘Controller Assignments’ window with the definition selected. You can learn a tremendous amount about the inner workings of control surfaces (at least I can) by examining the ‘Zone, Mode, Control, Parameter’ settings.