Dragging Mine Tower Area Tooltip Error

Issue description

Now mine tower areas, etc. can be resized by dragging their edges, the tool tip is no longer correct. i.e. a click drags the edge rather than adds a point. See attached image. Additionally, I suggest when dragging an edge, adjacent edges should stay at fixed angles.

Reproduction steps

Adjusting a mine tower area.
Look at the tooltip.

Game version and build number

v0.8.5 b598

Operating system

Windows

I think the problem may be caused by arthritis.
My clicks are not fast and are being interpreted as a very short drag, so does nothing,
I have to double click to get it to add a point along the edge.