The gold standard for levelling the bed on a resin printer seems to be using a sheet of paper.
Is there any reason why is can't be done by lowering the bed to home while the FEP tank is in place and leveling it there?
I'm specifically thinking of the Elegoo Saturn, where the bed is levelled by undoing two bolts and moving it to home, and then tightening the bolts.
For situations where everything is covered with wet resin and you don't want to have to clean everything up or to risk getting resin on your glass. Not for everyday levelling.