I found it while mining through the nether regions of the software. It goes like this:
From green menu bar open 3 dots screen, tap
settings icon, tap
troubleshooting at bottom of screen, scroll down, find
routes menu, select
delete all routes.
Obvious really - not.
IIRC you can delete all tracks and all POIs from the relevant screens. If you want to delete some but not others you are still down to finger tapping like a demented woodpecker - no such thing as a tick box in VR.
Edited to add: if you want to do the same trick on an i-pad the delete routes function is hidden in a different place. It is in the Help & Feedback menu. Are we sure VR wasn't designed by a government committee?