Well, after some searching in various places, I found this:
Setedit.com
Select the version "SetEditFDU". I don't see any hack information on the site, although there might be some, so please delete this link if any is found.
This is a channel editor for .FDU files that *seems* to work well with the current version of .FDU files that the Visionsat uses. It is a demo version, and requires a rather steep registration fee (19 euros = about $40) if you want to use it to make more than 20 changes after it is installed. It seems to have many features, however, I can't seem to figure out how to add a new satellite. I will continue to play with it as long as it works (I have 15 changes left). I did use it to edit the "USER" satellites in the Visionsat list to give them orbital positions, so USALS *should* work on these now (I changed them into Hispasat 1c/d, Intelsat 3r, Intelsat 9, and Galaxy 27). If I discover how to add a satellite, I'll post that info here.