There's already a way built in to the operating system to save or make favorites for Google Maps.
What I did was made a folder on the home screen by holding down on any clear area and called the folder Map Favs. Then again on the home screen, hold your finger down on any clear space till add to home screen menu pops up, select shortcuts, then directions.
Here you enter in destination, navigation type (car, pub transit, or walking), shortcut name, and select shortcut icon. Once you save it, this creates a shortcut on the home screen. Then you can hold it down to where you can move it, and move it to the folder you had made before.