How to run multiple steam accounts in a sandbox with one batch file?

Question

cmd/bat

Hello!
You need a batch file to run several Steam launchers with an already entered login and password. Write please)

Answer 1

Well, Steam itself is resisting it. So either reverse engineering steam.exe or nothing.
The rule is simple:
1 sandbox = 1 steam account.
We'll have to run a few sandboxes.