It's not possible due to the different projections used.
You can, if you like still do the same - albeit manually.
If you right click on a Google maps page in the browser and choose 'what's here?' from the pop up menu, it will give you the co-ordinates in this format (51.439323,-1.075158) - just paste that straight into the Add Waypoint menu - ignore the fact that the format is not as specified... it will work.