Does anyone know how to assign a rotating/slider joystick control to the trim controls in FS-X? I have an X-52 joystick that in FS9 I had one of the rotating knobs assigned to this, and I can't see any way to assign it with the new version.

Yes, I have two rotary analog controls assigned to elevator trim and mixture in FSX they both work fine I also assign the brakes on my rudder bar this way.(I use a TM HOTAS Cougar system with a CH rudder bar)IIRC you do it exactly the same as FS9 go to options/controls and select the appropriate tab at the top I forget the exact name but it has the joystick axis assignments displayed in it, the throttle and the stick axis should already be assigned. Just pick the control you wish to assign then tweak the knob you want to use until it is picked up by FSX. Don't forget to go to the sensitivities page and set the sensitivity and null zone or you may find no response as the sensitivity may default to the zero setting.Have faith it is there, sorry I couldn't be more specific but I am not in a position to kick off FSX and check whilst I am writing this. Good luck

than to the commands and controls. I have been able to assign the prop pitch on the throttle joystick (Saitek 52)to "axis X", which is the knob on the right underside.