Google Maps: How do I start a route that I’ve saved to My Maps?

How do I start the route? As in: get directions, traffic, time estimates, navigation etc? At the moment I’m looking at the saved route on the map and just copying the source and destination locations into a new directions page on Maps, but this obviously doesn’t give you the actual same route that you customised on My Maps.

https://webapps.stackexchange.com/questions/90918/google-maps-how-do-i-start-a-route-that-ive-saved-to-my-maps