Yes, List() gives you a list where the elements are delimited with a ¶. The usual method to turn that into a line is:
Substitute ( theList ; ¶ ; ", " )
No need for a script, though; you could define a calc field to hold the result, e.g.:
Substitute ( PortalTable::combinedName ; ¶ ; ", " )
Of course, instead of ", " you can use whatever separator you like.
And if you only need that in a letter (?), you could incorporate the logic into your Letter script to put the result into a $$variable and do without that calc field.
Thanks again erolst this works perfect!