Pretty cool,
I don't know if you heard of "lapdocks" which could come in handy as well.
I wonder if this lapdock for instance would work for you ?
https://www.carousell.sg/p/hp-elite-x3-lapdock-android-compatible-201708364/
The question I have in terms of compatibility is if GrapheneOS is recognised as a regular Android by a monitor. In which case you only need to make sure your monitor or lapdock is "Android Compatible".