There is a situation, you have saved several places in Google Maps and you want to display all those places in one map in Google Maps. How to do it? It is a way to do it, by using My Maps. However, there is no way to add them through My Maps directly. Here the tips from this link to do it:
- Export them using Google Takeout
https://www.google.com/settings/takeout - Export them from “Google Maps (My Places)”, not from “Bookmarks”. They will be downloaded as a GeoJSON file.
- Use this site to convert the file to KML GeoJSON
http://nearby.org.uk/convert-saved-places.php - Once download the KML file, can import it into the custom map.