It would be good to have a strong password option instead of pin for other local users.
Given that managed users are part of your account, they already have a regular strong password or even 2-factor authentication (=yours!).
The pin is only required to pick users inside your home.
There’s an existing feature suggestion asking for longer and more complex pins. I suggest you comment/vote in that thread in order to avoid distracting/dispersing votes.
I see that thread is from 2016, come on plex team lots of threads dangling like that. When are you going to give it?
2022 clean-up: duplicate