GeoNames Map Explorer supports Spatial Bookmarks/Placemarks/Waypoints
You can record where you parked your car or your favorite spot
you can also add a GeoNames location to placemark.
When you add a placemark, you are asked for Name and Notes
Automatically MGRS and GARS GRID is calculated and recorded for placemark
Placemarks can be Exported as GeoJSON and can be deleted