Extracting Transit Layer polylines (e.g. subway lines) and using them in Google My Maps?

I am trying to create a Google My Map of Tokyo Metro and Toei Subway lines. So far, I’ve been painstakingly drawing the subway lines manually, only using a mouse. Here’s what I’ve got so far (WIP, of course). It is extremely labor intensive to do it this way, and I am convinced there must be a way to automate this process, even if it requires utilizing the Google Maps API or even Google Earth Pro.

Here’s another example of the kind of thing I want to do, though obviously not at this scale: https://japonyol.net/editor/ajax.html

Does Google Maps allow you to take a polyline object from the Transit Layer (e.g. the polyline of a subway line) and add the object to a Google My Map?