Oh, I just realized that I was answering the wrong question. You were specifically asking about finding superchargers
along the route. My apologies.
On a PC, you can get the route shown, and there should be a row of buttons at the top of the map area. Mine had buttons for Hotels, Gas, EV charging, Things to do, and Campgrounds. There is also a More button that will give you a search box allowing you to enter "Superchargers". The search will apparently not always cover the entire route, so you may have to zoom into a section of it and click the "Search this area" button at the top of the map area.
On a phone, you can watch this video to see how to get to the function that allows you to search along a route.