Just to complete what Kevin said.
At this time, it is not possible to Save only a Kit. You can only Save a Project that includes the Kit.
However, it is already possible to load User Kits either:
- using the big knob in KIT mode this will scroll through all the Kits from Factory and User Projects)
- In the LIBRARY screen / Edit current project, you can drag&drop either an entire Kit or individual instruments from the Library (lower part of the screen) to the Current Project (upper part of the screen)