When the Push update with the 64 pad layout came out, I made a tutorial showing the quickest way to combine Drum Racks for it. Recently Sonic Bloom follower Pol Tow shared his way to quickly throw together Drum Racks. It's not actually combining them, but done with routing and the creation of a group track preset. Since it's even faster than my solution, I thought I'd share it here with all of you, although it does not functions differently and has a few drawbacks. Either way, it's up to you which approach you prefer.
If you have any questions or suggestions, please make use of the comment section below.