If you want to get really into it QGIS is pretty much the best way to make custom maps. It takes some work but you can make very specialized maps. You can import a lot of information and some of the information can be made by you.

The only good example I can think of off hand is importing tracks from something like organic maps. Allowing you to plot trails without requiring internet. (Probably still requires gps from your phone)

It’s probably overkill most of the time tho