As said above there is just the reference_points.cfg needed. It defines where the cable should attach, just like an interactive point or a contact point. Other than that the type has to “glider” and the layout.json has to be updated for MSFS to “see” the new configuration file 
The same thing also works for towplanes - they also got the reference_points.cfg in place to define their attachment point. Anyway these may need as different flight model. On tests the behaviour of normal user aircraft like the DR40 was pretty strange (e.g. way too high AOA on takeoff resulting in a stall).