I don't think you can connect two shifters at once. The game would recognize one only , as it should. It doesn't know what the other shifter is for. That would be like hooking up two wheels , or two sets of pedals. You don't want to do that.The problem occurs when I connect the fourth device.
I would like to connect the two at the same time to not have to walk connecting and disconnecting. Also because when I use one, the other the need for other functions.
sorry for my English. I hope you have understood me well.