SAP Message UM055 - Menu & refers to an external menu. No further entries possible.

Diagnosis
You tried to enter a new application area. However, this menu refers toanother menu.

System Response
It is not possible to enter more application areas with it.

Procedure
If you want to maintain this menu individually, first remove thereference to the external menu. Place the cursor on the entry 'Choosereference menu ...' and choose the function 'Delete'.