Hello Robert,
Yes, the Horizon Editor application gives/uses the "theSky 6" format.
I don't own and don't have access to TheSkyX so...if you could provide some information about the format TheSkyX uses (you said that you were able to convert it by hand) and are willing to test, i might be able to update and compile a new version of the HorizonEditor.
Regards,
Jörg