Why I see as names for OS objects only question marks when I use the µC-OSII add-on of UDE ?

The question mark '?' is the standard name for all OS objects in µC-OSII.

You can assign names with the µC-OSII API functions OS*NameSet(...) (OSEventNameSet, OSFlageNameSet, OSMemNameSet, OSTaskNameSet). Please note that OSEventNameSet(...) is used for all synchronization objects (Mutex, Queue, Mailbox ...).