A pivot point is an already calculated point on an isochrone from which we wants to resume routing.
Routing with a pivot point allows for very quick routing study as it soes not require to recalculate the entire routing and you do not have to edit the route.
Lest us take an example where we sail from Laredo, Spain to Concarneau, France. We set sails on Thursday, November 26 sailing a Sunfast 3200 in  a high pressure system.
What would happen if we decided to keep sailing on port for four more hours at the beginning of the trip ?
Let us zoom towards the tack zone. Grey points appear on isochrones. They are the potential pivot points.
Let us long press a point 4 isochrones further such that we would sail upwind on port. The app offers to create a pivot point and to resume routing from that point.
We would sail for 4 more hours by delaying the tack…
The isochrones from the first routing are displayed again at the end of the run such that you can launch another routing with a pivot point.