I have been using shapr3d a little now, I don’t know if you can draw construction lines or change a line to construction line. This is very frustrating because when you have to select an area in the drawing and you have line that was there for construction reasons, there are too much area to pick to just select the area you need. Hope this makes sense, I am using an iPad Pro, I use different cad software that have this feature.
Are you referring to guide lines, like in a program like vcarve you can add guide lines for the purpose of measuring and arranging? This would be great to be able to toggle on and off, especially if they do not get selected when selecting an overlapping line