The advanced manual doesn't cover everything in specifics. As anyone who ever owned a NICAM VHS recorder knows, how many of us could understand all of the detail in those manuals? Most pages were never read.I checked out the manuals for the G85 and GX85 (a particularly dull and confusing task if you don't own the camera and can't "play along") and neither specifically stated anything about saving any image stabilization settings to the C slots, nor did did I see a listing of what settings can't be saved. I find it hard to believe you can't even turn off IBIS in a "C" slot, but this is a "WTF Panasonic???" thread, so I guess I shouldn't be surprised?
I haven't got my G80/85 close by right now, but on the GX8 I can store the IBIS settings to taste in C. I have for instance switched off Left-Right IBIS detection for sports and BIF mode in one of the C settings. I even have the Fn keys reconfigured for different C settings.