The GDL implementation in AC9 adds the option for the object designer to make edges detectable in plan for the purpose of selection.
Detecting Cutline JAM9
This ability can be added to any line or arc. I'm working it into the libraries gradually, going for maximum convenience and minimum nuisance. In addition the cutline above, all the JAM9 trim tools are detectable by the front edge. This should make easier to select trims, which tend to coincide a lot. I am listening for suggestions.
Look closely at the image above and you will see that the special snap points (midpoint, etc.) show up on these edges.
Remember that this is only for detection. There's no polyline editing ability. You can use such edges for splitting and adjusting, but not Cmd+clicking. (Yes, I reported that.)