You think that by trying to screw up a very high end Garmin unit it would be faster???

Plus this can not be done even if it is a Android based unit as Boki_Srb points out.

Because the route calculation time is very long.
on a 2000km route I use somewhere at 20 intermediate points
and it always takes a long time to change or add a waypoint
I have a couple of Garmin units and I plan all my waypoints in Mapsource and add them in to the Garmin on any and all trips I make.

Once I have reached a waypoint I just pick a new one that I installed.
You can even change your plans and bypass a waypoint and pick one of the others.

When I am done with this trip I copy them to my Laptop for use at another time.

Also plan ahead for trips.