To join a UCS user with an existing o365 user you have to save the Azure-users objectId in the UCS-users UniventionOffice365ObjectID attribute.
There is no automatic way to do this. You can contact our support however, and they will help you with the process.
Hints:
- The UCS-users
UniventionOffice365ObjectIDcan not be edited from the UMC web site, but from the command line. - The Azure-users
objectIdcan be found on the Azure website among the users attributes.
Greetings
Daniel Tröder