What you describe is normal behaviour.
I am confused by Trados. In the tutorials the MultiTerm-Window works just fine. You open a segment in your source-text and the little right hand window of the Trados Workbench shows a couple of terms found in the Sample Termbase.
Presumably, these refer to the same concept (i.e. one red line)?
In my case this does not work at all. I created a termbase, filled it with a few words (OK = Ok, Cancel = Abbrechen, Next = Weiter and so on) and then tested how Trados would react when opening a segment that contained all of these. It shows a red line above the terms and one entry on the right, but that´s it.
That's as designed - the term recognition pane in the Workbench window only shows the current term, although it's possible to have several entries shown there (where several terms exist, for example - let's say your termbase entry for "OK" has two target terms, e.g. "OK" and "Bestätigen").
To insert (and display) the next term, use the corresponding command or shortcut (e.g. Alt+RightArrow).