Hi,
At the TGP there is a thread about you have to select a rig and save the cab in order to use that cab in another rig. From what I have heard this will be made easier in future updates.
BUT ...
There is another way to do it already that not many people seem to consider and that is browsing speakers/cabs using the lock function.
1. Select the Rig with the amp you want to use.
2. Use the Lock function to lock everything in that rig you want to use. That could be everything but the speaker/cab.
3. Then change to another rig. As you have locked the amp (and maybe all the stomps and fx) all that will be loaded from the new rig is the Cab. This way you can easily browse all the cabs in all your rigs available in the KPA. No need to spend time storing a lot of stuff unless you really want to "catalogue" your cabs.
I use the lock function often and think it's a killer feature.
Cheers,
Mats N