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