Hi @panterra,
Do you want to filter your CDS records created by current login user?
Actually, the 'Created By' column (System column) is a LookUp column in each Entity, which looks up to User Entity within your Common Data Service. In addition, the 'Created By' column link the corresponding user in the User Entity through a unique GUID string, e.g. '0342f767-4414-e911-a981-000d3a828979'.
If you just want to filter your CDS records based on the unqiue GUID string (OID value that you mentioned) of the current user, I afraid that there is no way to achieve your needs.
Currently, within PowerApps, there is no direct way to get the unique GUID String value of the current sign in user within the User Entity. You could only get the unique GUID string value via the Email Address, Full Name or ... of a user within the User Entity.
As an alternative solution, you could consider take a try to filter your CDS Entity records based on the email address of current login in user. I have made a test on my side, please take a try with the following workaround:
Set the Items property of the Gallery to following:
Filter(TaskLists, 'Created By'.'Primary Email' = User().Email)
On your side, you should type:
Filter(YourCDSEntity, 'Created By'.'Primary Email' = User().Email)
Best regards,