Start more restrictive session in the middle of another session

I don’t know if this has been discussed. Or maybe even possible already. Please point me in the right direction if so.

It would be lovely if I could start a more restrictive session in the middle of another session. I have a scheduled deep focus session every workday that blocks a bunch of entertainment apps for a couple of hours in the morning. Normally that’s sufficient, but on some days I’d love to be able to start another, more restrictive session that whitelists only a couple of writing apps before my scheduled session is ended.