I got a leak on my shimano 105 R7020 STI
According to the ST-7020R exploded diagram at
https://dassets.shimano.com/content/dam/global/cg1SHICCycling/final/ev/ev/EV-ST-R7020-4341C.pdf
That part doesn't exist as a removable part, hence why you need to confirm your exact shifter part number.


For completeness - the dealer manual is at https://si.shimano.com/api/publish/storage/pdf/en/dm/RADBR01/DM-RADBR01-07-ENG.pdf
and a browse through shows no mention of removing that plate.