When a string, use that string instead.
When a face, use the standard 3 dots, but with the specified face.
The change affects only Org-mode (which will then use its own display table).
-Changing this requires executing `M-x org-mode RET' in a buffer to become
+Changing this requires executing `\\[org-mode]' in a buffer to become
effective."
:group 'org-startup
:type '(choice (const :tag "Default" nil)