I asked the same question and 'johnmandy' kindly came up with this solution which works suprisingly well.
See his solution below:-
I have created several routes on the 2800, as previously stated you can definetly add/remove waypoints.
My approach is as follows:- Using the map you need for drawing a route on your 2800, zoom out enough as to be able to cover your route,
don't worry if its not completely accurate, as you will see later.
1/ Open overlay/settings menu.
2/ Tap overlay.
Start drawing your route, easier with stylus, my approach is to put in too many waypoints, again don,t worry if its not too accurate, remember to double click on last waypoint. once completed, zoom in to the start of your route and using the stylus select each waypoint if needed and move to the where the desired route should be. When selecting each waypoint do not dwell on it too long before you move it or the waypoint property box will open. carry on with this method untill you reach the end of your intended route. if you have too many waypoints left, tap and hold desired waypoint, a waypoint property box will appear, you can then delete that waypoint. Carry out same procedure for the rest. You can use the previous structure for adding waypoints.
Finish by saving your route, hope this helps