https://greasyfork.org/en/scripts/533463-openstreetmap-gpx-overlay
I often need to check OSM tag information of the roads along GPX routes which required frequent switching between osm.org for queries and a GPX editor for the path, so I made this userscript which adds a button to overlay GPX file(s) over osm.org. It is nothing fancy but gets the job none: routes and tracks are displayed as polylines and waypoints as markers.