Here are photos of how I mounted the Garmin Zumo 550 GPS on 2017 C650 GT. Power cable goes to two port USB in power socket in left side cubby. Seems to be very secure on rougher roads
1) Nice central positioning, and looks good.
2) If your cable is sort of mushed in between a cubby door edge and its door frame -- this is not clear to me, if that's the case -- and you get tired of that placement, you might want to look into 3BR Powersports (
https://3brpowersports.com/) rainproof USB ports, for an external port. This will require some tupperware drilling, but I've done that on my last four bikes now without issues, using their products.
If you're interested in, or just curious about, this sort of setup, I describe the products and the process in the gallery for my C 400 GT, which I bought this past June, starting at this particular image and caption, and running for the next ten or so pics: