I believe there are no easa regulations on this and any requirements would be found in the AIP and / or on Jeppesen page 10-1P, or equivalent (General / Arrival / Taxi / Parking etc). In some cases this will also be regulated by your company in OM-A.
So yes, you can park without marshaller if the airport and your company allows it.
From Luton EGGW 50-1P
1.5. PARKING INFORMATION ACFT parking on all stands is only allowed with marshaller.
CP