Your answer, maybe accurate, but it doesn't answer the primary request to do off-line editing. Plus, restricting off-line editing to SD cards is too restrictive. Since UC Control, Capture, and Studio One can talk to a Series III console from a PC, it would seem the base structure is in place to do off-line editing and move files from one PC to another via thumb drive. Basically, it's an externally generated project/scene to be uploaded via UC Control. Just need a template.
I'd be happy with running UC Control (Surface), specify the desired console, and then enter the desired plan info: channel, User Layer, FAT Channel, Audio routing, digital patching, etc. Store as a backup file. Copy to a thumbdrive or SD card, Load onto destination PC or to the console via SD card, and there it is. Perhaps not the most efficient, but better than not having this capability.
In fact, the starting template could be a backup file. That would have the necessary physical info, e.g., console type, networking info. So what is needed is rather simple...The ability to read and write a backup file without an actual console connected.