Use Route Planner to Plan Trails

Click "Create a Route"

Click "Create Personal Route Plan"

Click "Get Started"

Click the map and navigate to where you want to add the trail.

Hold down the ALT key to freehand draw the trail. Otherwise it will snap to existing trails.

Press ALT and click points on the map, to route between.

Continue clicking and adding points while holding the ALT key.

Double click the last point and click "save".

Click the "Title:" field. And add an appropriate title.

Add the route to a project map collection.

Click "save"