Hi Martin,
Thank you for helping my sanity.. :-)
Looking at the code, the search help is a local single role and the local logical system name is used.
I then ran it in the debugger to see where the "target system" = "user system" is coming from when adding a single role and hitting "enter".
Well, well, well... the plot thickens... Yes, the assignment of the single role itself is the same as the logical system of the composite role, but those single roles themselves can have "target systems" for Trusted RFC. This means when the user menu is turned on and the user in the system where he has the composite role clicks on the transaction from the single with the "target system" assignment, then the session_manager will via trusted RFC take him to that target system and start the transaction there (assuming he is authorized for the transaction there). This must additionally be turned on in SSM_CUST via switch TRUSTED_SYSTEM = 'YES' (default is 'NO').
So I am coming closer to the conclusion that this is just navigation for systems setup that way and actually has nothing to do with the CUA. The "target system" field will never assign roles from foreign logical systems and any alternate value coming into visibility there is actually an (optional) RFC connection for navigation for the user.
Has anyone ever tried this and survived? :-)
Cheers,
Julius