Disclaimer:

I do not know PrintMusic.

In the “full Finale” you can do this:

Simple Entry Tool.

Select the entry after the desired point of beam break.

Simple menu > Simple Edit Commands > Modify Entry > Break/Join Beam

At least in full Finale (and I suspect in PM) you can also plant the Speedy Entry cursor on the first note of the new grouping and press the slash key (/) to break (or rejoin) the grouping.

When you say couplets and triplets, are you working in 7/8 or notating a hemiola in 6/8 or are you dealing with actual tuplets?

It’s the same in Simple. Select the note that you want after the break, and tap the / key.