Yikes, that’s no fun to edit. Depending on how manually you’re going to carry out this edit, would there be any benefit to aligning any non-parcel areas to the parcel boundaries? I’m thinking of something like a schoolground (amenity=school or landuse=education) that would’ve been drawn in roughly according to the property line but without the benefit of this data. This would only be a good idea if the parcels seem well aligned and are suitably licensed. (I take it that this is the same parcel dataset that was used to prepare the Dallas building import.)