... maybe there is a way to completely LOCK a section of a score? Not just a "fit measures" lock,  but an instruction that completely freezes a part of the score, so that it cannot be changed, until it is no longer desired to have it freezed?

I think your best bet is to do them as individual files. Do your parts, etc. Convert them to PDF, and assemble them as a single file.

Yes of course, but it is a lot of pdf files to concatenate ... 8 parts x 10-14 = around 100 files. Maybe I'll do in blocks of 2-3 pieces/file. (It might even help with the structure of the whole piece to do so). 

Still, I do like the idea of having a "freeze score" option. Select n measures and one click blocks editing of those measures. might post it in the suggestions sub-forum.

 I think your best bet is to do them as individual files. Do your parts, etc. Convert them to PDF, and assemble them as a single file.

Best advice!

If you read my OP you should notice that I am well aware of that "best advise" "suggestion": I was looking for alternatives "other than keeping each piece in a separate file" (dah ...). The reason is that having to concatenate 80-120 pdf files is not so great (although one could write a little bit of code to do that automatically, but then having to test it .. etc..)

As I already mentioned a compromise is to divide the project in sections blocks of  3-6 pieces. That should results in more manageable files length, and will bring down the number of pdfs to concatenate significantly. 

Optimal would be a "freeze-a-section-of-the-score" option, then there will be no worry to keep everything in one file. But Finale does not seem to have it.

I've never heard anyone use 'concatenate' in regard to pdf files (SQL and Excel? yes). What exactly are you trying to accomplish? 

If simple organization, that's pretty easy.

... concatenate, bind together, make 1 pdf file out of n pdf files. It is a trivial operation, but error prone when n is large. Anyway, I already answered my original question.

... and thank you very much to everybody, but please stop trying to help unless you are not stating the rather obvious!

It seems to me that you already know the best alternative. One file is (IMNSHO) is definitely asking for trouble. And what’s the difference between “freezing” a section of the score, or breaking it up into two or three parts?

Never mind; you do you.