Removing a User from Quest Migration Manager

Hi All,

I am new to Quest migration so I apologise if this is a silly question. We have two domains that are trusted (1 & 2). We use Quest migration manager to migrate accounts from domain 2 to domain 1 (domain 2 was a company acquisition). Domain 1 then syncs these accounts to Azure via AD Connect. 

We would like to setup a direct connection between domain 2 and Azure via AD Connect and stop the quest sync between domain 2 to domain 1. Can someone explain to me the safest option to remove a user from quest migration manager, thus removing the user from domain 1 at the same time?

Any help is greatly appreciated.