Separate Landing sequence

When planning a mapping mission, if the landing area is in the path of the mapping mission it is very difficult to plan and modify the landing pattern for arduplane. Would it be possible to have a button that hides all the other waypoints before the "Do_Land_start" command? and when clicked again brings everything back?

This would making putting the landing after a mapping mission in, or any sort of complex mission, much, much easier to do.

Also, a button in the right click for Start Land would be good as well to make it easier to add instead of having to add a waypoint and change it manually.

Start by reproducing the mission-planning workflow with a mapping mission followed by a Do_Land_start command. Inspect the waypoint display and context-menu behavior around Start Land. Done means a control can hide and restore waypoints before Do_Land_start, and the right-click menu can add Start Land directly.

Written by the indexing model from the issue text.