I'm presently targeting things that have inappropriate 'layer' entries in my area.e.g.
highway, layer -5 ... no tunnel/covered etc ...
park layer -2
I assume this way done for rendering issues. The areas look to be best served with multipolygons.
There do not appear to be tools to find these inappropriate layers, so I'm using a simple text editor to find them., then JOSM to do the editing.