Settle3D > General Features
If at any time you make a mistake while entering geometry, you may "undo" the vertices of the boundary you are entering, with the vertex Undo option, as follows:
Select Undo from the right-click menu, OR
Type u followed by Enter in the prompt line.
Either action will remove the last vertex from the current polyline you are entering. Undo can be repeated any number of times to remove successive vertices from a boundary you are drawing – experiment with this option to see how it works.
NOTE:
The vertex Undo command is only operative while you are entering a boundary. After a boundary has been added, you can use the global Undo option (in the toolbar or Edit menu), to remove the entire boundary, or use applicable editing options to edit the boundary.
Vertex Undo is applicable for modeling options such as Add Polygonal Load, Add Wick Drain Region, and also drawing tools such as Add Polyline, Add Polygon.