Hi Tommy.
I read your question in 2 ways.
One way is to do them in the stretcher editor, you can adjust individual stretchers by highlighting and clicking on C or using the adjust stretcher dialogue which has two or more layers of additional controls.
Or are you referring to a top shelf stretcher.
I can't think of a way for global or directory wide modifications, but others may have a way to do it
I sometimes find modifying stuff like that a bit like Russian roulette, when it works its like wow, what an amazing program! That was easier than I thought and it just works. That was good.
Or the other scenario, this could work this way, why is it so hard? I wonder if I'm the only person to want to do this? And Damm!

now I have lost all my settings, Now I have to start over.
I try to (just like you are doing) find the best way first, then do a thorough check after modifying one cabinet first before proceeding onto modifying all of them.
Just a thought
You can duplicate a whole directory as well.and perhaps just modify all of those in that directory.
I find the placement of screw holes is related to the material. Particle board can have them a lot closer to the edge where as MDF needs the wider stretchers with different insets so you might want to keep your existing library ....
Probably not much help.
But good luck