Something like extendsrf for subd?

we do you create a similar topic for the same aspect ?

my 2 cents - - an algorithm might not guess what the user is after. Most scenarios will require to move or adapt the result…

regarding your straight option:

did you try
_slide (the input edge to extend the faces)
_insertEdge (“divide” the extended faces)
i think this is closest to what you re after ?

i would appreciate to keep one topic for one aspect - so if someone of mcneel might merge the topics ?