The way I do it is simply by copying/pasting the rig I like into any performance. All witin rigManager. Double clicking the performance sends it to the kemper.
There's a small bug (I think), where the name of the rig is not synced with the kemper. I usually force sync by double-clicking on a performance slot (disable/enable) then double clicking on another performance, and re-double-clicking on the initial performance where I pasted the copied rig. A bit painful and obscure, but it works...
Again, I don't have any rigs stored in my kemper. Only performances. All the rigs are on my computer, organised in rig Manager.