Tk-093,
I was in the same boat, I couldn't manually add the location I'm at, but I figured out a way without manually typing in GPS coordinates.
1. Search in Cortana "where am I" if you're near the location or for something else that'll produce a map for the area you want to mark. Note this is not a search in the "Places" part of the notebook, but in Cortana's general search.
2. Click on the map in the search results, opening a full map view.
3. Move the map to wherever you want a new place and hold your finger over that location. A black pin with the general description should show up.
4. Click on the new pin.
5. At the bottom of this page, click the Star+ symbol to add this location to Cortana's places.