Extending a trail

I noticed that a local trail, the Hastings Heritage Trail (formerly Central Ontario Railway) in OSM ends some distance short of its actual ending location. Even that location is artificial, it ends because of the border between two regions, the trail continues physically for some kilometres after that point.

I would like to extend the trail to its proper location. I want to ensure I do so the “right way”. I did a bit of Googling, but nothing very specific turned up. Is there a guide to extending an existing vector set the “right way”?

Do you mean https://www.openstreetmap.org/relation/7319029 ?