'Manager' attribute, unlike other attributes based on 'BROWSE_PROJMGR' lookup, does not behave the same in the Classic than in the Modern UX.
Steps to Reproduce
Expected Results: Both 'Manager' and 'Target Manager' do not return any values when expanded.
Actual Results: 'Target Manager' does not return any values when expanded (expected), but 'Manager' returns the same values as before the changes.
15.7.1 and higher
This was analyzed by Engineering and Product Management under DE64297.
The Modern UX is working as expected, it is using a different system-restricted lookup.
The Project Object, Manager Attribute uses the 'BROWSE_PROJMGR' Lookup. This lookup is defined as System-Type = 'User-defined'. This means the Query can be modified. Classic will continue to use this lookup as defined in Studio on the Project Object.
The API /describe/projects uses the 'BROWSE_PROJMGR_NAME_ONLY' Lookup. This lookup is defined as System-Type = 'System-restricted'. This means the Query cannot be modified . The API & Modern UX will use this lookup instead of the lookup defined in Studio on the Project Object. The new lookup was created to improve performance in the Modern UX.
On the Idea Object, the 'Target Manager' Attribute uses the 'BROWSE_PROJMGR' Lookup in both Classic and Modern UX.
If changes made in "Attribute Suggestion List Display" section of BROWSE_PROJMGR_NAME_ONLY lookup is not reflecting correctly in the Modern UX, try creating a dummy custom attribute in the Project object, that refers to this lookup. Then check if changes made to this section start showing against the "Manager" attribute or not. The custom attribute can be deleted after testing.