How to map multiple instances of the same form
are the invoice forms precisely the same for every single kind? purchase, credit note, etc?
If not, I'd suggest creating a persisten project level variable, and using those variables as a unique identifier within the name mapping properties of that invoice object within the name mapping repo.
So at the top , it may say something like (object type- something) for the form, but you can edit and add in additional properties, say perhaps a txt identifer of some kind, that points to that persistent variable that tells testcomplete which invoice form you want to perform the settext or keys operations on.