Indeed, the task sounds easily accomplished with ViewRanger, assuming @BobM has the GPX track for the route they want to plot. (If you don't, you can plot the route from scratch and drag waypoints to adjust accordingly).
May I also add this link that discusses (in French) the traditional walking routes across the Central Pyrenees between St Gaudens in the Comminges and Barbastro, complete with GPS tracks and assorted practicalities. It covers the way via Vielha, too.
This site is run by Ivar at in Santiago de Compostela.
This site participates in the Amazon Affiliate program, designed to provide a means for Ivar to earn fees by linking to Amazon