sourcing external read-only constraints files from within the QSF file

The problem stems from the fact that this was never meant to be the way the .qsf was used. For a quick history:

- Original it was broken into 3 ore more files, an .csf, .psf, and one or more .esfs. All of these files were meant solely to be storage files for Quartus, i.e. the user wasn't supposed to edit them. But they were ASCII, so no surprise that people started doing that. It did not work well, and users would close Quartus and sometimes have to delete their /db just to not mess things up.

- Everything finally got merged to single file, but Quartus re-ordered everything and removed comments everytime Quartus was opened.

- The re-ordering was fixed, comments can be added directly into the assignment, and Quartus plays much more nicely.

- The ability to spread assignments was added. I think this is especially useful so the user can decide how to break things up, i.e. have a pinout file, a timing file, etc.

The problem is that I just don't think the infrastructure is there to intelligently know where things are at. Meaning, if you have all pin assignments in one .qsf that gets sourced by the master, and then change/add a pin assignment in the GUI, should that go into the master or the sourced one?

Now, I'm not saying it couldn't be better(especially the one about syntax errors issue), but I think you're running into the current state. You should file some SR/s so they at least hear your complaints. I'm guessing to do this better is a pretty large re-structuring internally, but it could definitely be improved. (I love TimeQuest's SDC files and the fact you can script anything and have complete control, but the downside is that the GUI interaction is limited.)