This works, if in instanttranslate you do not get a result from the TermPortal.

Yet if you get a result from the TermPortal and you get a translation from MT, that is different to your result from TermPortal and you try to add it to TermPortal via the available PLUS icon, then you switch to TermPortal and the Term is selected, that was the result of the TermPortal result in InstantTranslate, but nothing is offered to add as new term.