Well, something like this:

Create and move freely the points that form the "broken line" (even though it looks smooth) with the mouse by clicking in a nice GUI with many visual and data handling options and functions (zoom, colors, cut-copy-paste, undo are just a few that come to my mind rapidly).

Also with the mouse, set the smoothness factor of each point (that would affect the concavity of the adjacent lines).

By double clicking in a point, an exact value of coordinates could be entered by text.

In addition, it could have a text-based-point-creation control panel, where could be set the coordinates where the point will be created.

Finally, a "export to text file" function with selectable resolution. (May be a "send to PD + "arrayname"" would be ok too)

This is what comes to my mind. May be it's too much. Should I try to build this in PD or I should use another language? In that case, which one?