Lock Button Question....RIg?

Today while noodling on my Kemper, I pressed the "Lock" button, while in "Browse" mode, to see if I had any modules locked. I didn't, but I noticed that the rig button lit when I pressed the "Lock" button. I could also toggle the rig button on and off while holding the lock button. Can someone tell me what this is locking?

Thanks. I didn't know that