OpenStreetMap Notes [1] enable you to add a comment on the map to assist others in mapping/editing OpenStreetMap.
They are not for personal notes, I'm thus closing this note.

If you want to make a marker on a map to share with a limited circle of people, then uMap [2] might be good for you.

[1]: https://wiki.openstreetmap.org/wiki/Notes
[2]: https://umap.osm.ch/