You may be interested in Private Spaces, which are, in a nutshell, user profiles nested into the main user or another secondary user which can be used without switching. You lock / unlock as you need it.
Discussion
Seems like insular
This is an app that uses Work Profiles for the same thing, a Private Space provides that environment without needing an extra application to do it. It's an OS feature and works better.
You can have a User, Private Space and a Work Profile at the same time.
Hell yes!
Yes, but it seems you can't block internet access......
User profiles like Private Spaces have their own VPN configuration, files, and their own credentials if you want that. In this example my Private Space runs a different VPN and a different instance of Molly (Signal) from a separate burner number not on my device. You could use it for Wallets, for using Tor, I2P, whatever you want. Realistically people use it to put Play Services and apps that use it in it when they don't want to put it in Owner.
GrapheneOS provides some improvements to it. You can have Private Spaces on secondary users, not just Owner. You can also toggle clipboard sharing including import/export control. You can also make it "End Session" on lock, which puts the profile at rest and securely powers it down.
Interesting, as GrapheneOs user i use shelter app to have work and personal "private Spaces" also in my Owner profile. Is that similar from tech point of view?
What these apps do Private Space does and better. You don't need to install a third party app either.
I am sure about it. The only good thing as user is that you don't have to switch to a second user every time. But i am sure grapheneos does it better!
Private Spaces are the exact same UX wise as work profiles. You just access the space at the bottom of the app list rather than a tab at the top of it.
How do I activate private spaces?
Settings app -> Security and Privacy -> Private Space
If on other Android OSes it may be elsewhere. Search "Private Space" in settings.