Just start the Mir4.exe directly inside a sandbox. Doesn't matter if it is steam or global launcher. Free to use https://sandboxie-plus.com/
For each account you need to create 1 sandbox and run the game inside it via right click on the mir4.exe and press start sandboxed. After that select the sandbox you want to run.
Do NOT forget to create X amount of sandbox beforehand. There will be a couple of errors that sandbox will show you but you can ignore those.
If you want to run multiple accounts at once on PC use https://sandboxie-plus.com/ and create a sandbox for each client. If you installed the Game via Steam go directly into the folder where the game is saved and run the Mir4.exe inside a sandbox from the prog.