Reset session variables after switch to another configuration?

I recently add nesting.clone to my nixos configuration to switch between variants of my system. Everything works fine so far except the session variables: I need to reboot into the selected configuration to get the right variables setup, rather than simply activate it using switch-to-configuration.

Is that possible to reset session variables? I tried to log out and login again, but this does not have any effect, because the session is not actually restart I guess?