Map EditorRedid the bridge area calculation.
This was marking an area equal to the line drawn but bridges are drawn from the start point to the end.
SnapLine
Some refinement of the line terrains process.
Added areas.
Like when you're drawing these freehand, areas are self closing and to draw a square you draw a U.
For example:

Translated to a Field gives:

The dashed line is from the last point clicked to the cursor.
That screen grab doesn't include the cursor.
Not everything can work with this - removed those terrains which will not from the combo
Seems stable now.

I wasn't particularly careful drawing the lines there.
If you draw a line doesn't look right you can reset.
Drawing a line precisely around a field or next to another is a bit fiddly.
Since these are translated into regular terrains you can of course also delete one after you translate.