A new field for "domain" against the Contact record in CA Service Desk Manager/IT Service Management would give extra clarity where domains are involved. In particular, for large multiple-domain setups.
One instance that cannot be handled by SDM/EEM currently is the case of one CA Contact "userid" matching to multiple domains. If this is done, EEM will return multiple records that match that userid - but not know which one to use (AHD04013). See User is unable to log into CA Service Desk Manager (CA SDM) with domain credentials
If the domain was specified, then EEM could have clarity to make a match.
It would also give clarity on the domain field. There would no longer be a need to combine the domain and username field.
It would potentially allow other uses, such as a clearer domain, user, password on the login screen.
Note. This Idea is along similar lines, but a little different, to these two Ideas. They fall into the same family though.