Can multiple users work on the same assembly?

Without some kind of PDM, you have to develop a colaboration environment.

Put shared libraries in a search path, and segregate the project with defined responsibilities.

Basic rule: two people cannot put a hole in the same part at the same time, obviously.

Typically, I segregate at specific assembly levels and assign one person as an "integrator" for the next-level assembly to do the finish work.

I've used this method for over 30 years beginning with Cadkey patterns which were assembled into a full assembly part using Cadkey's "lisp" style program.  We had 3 engineers working successfully on a single project.

In our experience, multiple persons working on the same assembly is a disaster waiting to happen. This is due to the "last one to save wins" aspect of saving. If two of the people saves the same assembly (or part) file, only the changes made by the last person to save it are stored in the file. The next person to open the assembly will see the file state as it was saved by the last person. We've had people lose hours and hours of work because someone had opened the same file earlier in the day, then made a minor change at the end of the day and saved it, overwriting all that was done to it by the other person working on it.

Probably working on sub-assemblies but not the top level assembly would be okay, but:

(1) Proper discipline must be observed, as noted previously.

(2) Any one with the next level assembly will not see the changes you make unless they "re-load" the sub-assembly.

It's a messy situation. I don't know how it would be handled to avoid clashes.