I have a 350qx3 with a gopro gimbal hooked up to control from my dx8. The quad has two servo connectors in it and one is occupied with the gimbal. So my question is could I control another device like a servo along with the gimbal at the same time?
I am little confused by what you wrote, but here is a simple answer:
If you have a free slot on your receiver that you are not using then yes you can use a video switch. if you want one that has three inputs then you need to have a 3 position switch open, if you only want two, then you need a 2 position switch open on the dx8. If it were me I would not use the same channel to control both the gimbal and a servo, but rather use one channel to control the gimbal another channel to control the servo and mix the channels in the radio itself.