I have installed the Geolocation Field module, and added a Geolocation field to my content type. I have chosen Geolocation Google Maps in the Manage form display, so you can have your map, click on a location, and when saving the node, the latitude and longitude will be automagically added to the node.
I would like to add an overlay to the Google map shown in the admin form, but not sure how can I achieve this. I have seen the module Leaflet, which allows to add an overlay, but it is in the frontend,not in the backend, and do not see the module having the widget mentioned above for adding locations directly by clicking instead of typing the coordinates.
Any idea on what my approach should be? Even if it was to write my customo module, I have no idea how to approach the problem.