Agent Kits like SPJD are locked. You can ‘remix them’ and apply different mic/effect scenarios, but those ‘agent kits’ like that aren’t meant to be heavily edited. The idea is…you’ve hired Simon to bring his favorite kit (mics, sticks, techniques) and play for you in a studio session. You’re not meant to ‘use a different snare’ since it wouldn’t be using the same sticks and playing technique.
See this post for more info:
In contrast, if you build your own kits from scratch using your own samples, or starting out with the beat agent kits, or using any of the many unlocked samples that come with Cubase…then you get way more editing features.
There are ways to mix and match the Agent kits…
Say you want to use a Snare from a totally different kit and a ride from yet another.
Simply load both kits in GA. If the snares happen to be on the same pads it’s super simple. Have both kits on the same channel, mute the snare pad in kit 1, and solo the snare pad in the second kit.
If the pads don’t align, you can unlock the pad mapping and add/remove trigger notes for various pads.
You can also just put the kits on different MIDI channels. Use different MIDI tracks to begin with, and you can later freeze the tracks and merge them into one if you like (channel set ANY so things play over the right channels).
If you have Cubase, you can also use the track Drum Map and alter the outgoing channel of individual kit pieces.
See this thread for more info. While it was done for GA4, things are still very close: