I have done some things in a post processing on GetRows (for other tables… not GL) where I did a BPM that simply removed the rows that we didnt want to show… for Vendor.GetRows, we wanted to hide a specific set… so we put the following line into a C# block:
ttVendorList.RemoveAll(ttVendorList_Row => ttVendorList_Row.GroupCode == "PTNR");
maybe you could do something similar to the returned rows from GLAdapter?