Method 1
Reversing a Track
Home screen > Apps > Tracks > Active tab > Select the segment you want > Three horizontal lines in top left corner > Save as Trip, selecting 'Finish to Start'.
Back to Home screen > Apps > Trip Planner > Scroll down to Unscheduled Trips > Select the journey, check it on the map (just to make sure you are happy) then select Go.
Method 2
Reversing a two point (Start point to End point) Route from A to B created by you on the device.
Home screen > Select route, do not touch map or Go > Three horizontal lines, top left corner > Edit Destinations > Touch the start point (the one with the green flag) on the right hand end and drag it down to beneath the end point (the one with the chequered flag) > Save. The route will now display, maybe offering you an alternative, too. If there is an alternative, choose the one you want to take, then > OK