... in Windows. The desktop gets cluttered. You can only open one instance of the program.
While not arguing whether Win or OS/2 is the better OS for app development, I did ponder the "can you open multiple copies of same app, under windows" piece. I believe this is dependent upon the developer of the app, and if they restrict it, or if it doesn't make sense for there to be two or more copies of their app running under windows, there could be difficulties?
Launch a windows app, and then hold shift key and click the app on the windows toolbar, and see if a second copy of the program launches ... if a very specific program doesn't seem to work well with this method, then the developer may be checking for and restricting a 2nd running copy. In which case, we have to cheat ...
Use Sandboxie Plus, or create a 2nd acct & have that acct run another copy on the same machine.
Or, my personal favorite (a bit biased here) is to use virtualization, and just spin up multiple vm's running the same program, all accessing data on the shared filesystem space. Works for Windows, and for OS/2 (just not needed in OP's case) ... could be a tad expensive in licensing costs, though.
OP has a good scenario for *why* we use OS/2 instead of Windows, and I'm adding it to "the sales list" ... alongside OO desktop & such, where things just aren't as polished under Windows, to this day. Such examples make it easier to show OS/2 strengths to someone who thinks in only Windows or Linux terms ...
Hope this helps ...