Allow confirming a choice while navigating the context menu for nested entries

[bruno-f-cruz]

Navigation of the context menu of an operator with the keyboard arrow keys is very intuitive. However, there seems to be currently no way to "lock" or confirm a selection for nested entries (like Strings or Lists) since "Enter" seems to have the same effect as "Right" by going down the hierarchy of the menu.

With the goal to afford a keyboard-only coding experiment in the editor, I think it should be possible to use the "Enter" key to confirm ANY selection (if available). It should be noted that the context menu can already be opened from any operator with the standard Windows shortcut (Shift+F10).

To reproduce:

Attempt to use keyboard only to member select Item1