BeyondTrust and SimpleHelp both support this functionality. You can invite a second technician to join the session. I suspect all they’re really doing is opening up a second session at the same time, but the end result is that you can have two people remotely controlling a single computer.
But those are both “tech support” focused tools, so I don’t know if they quite fit your use case. Parsec is another option that specifically advertises collaborative work like pair programming: https://www.youtube.com/watch?v=XA21BnUsBJI
Oops, didn’t notice which community we were in 😂