There are any many fields and places, where you have to choose a worker or a global address book record.

In the dialog you can use the arrow keys to walk through the list.

The "Select" button shows the keyboard shortcut "Alt+Enter".

But the dialog does not react on the short cut "Alt-Enter"

Microsoft Support was able to reproduce the issue, triaged it with "we're unable to fix the issue now due to the magnitude of the fix, other priorities, or both", and recommended publishing it as idea.

The workaround is to use the mouse. If users have to do similar tasks all the day like setting a responsible person in forms. it would be extremely helpful to do this with shortcuts.