Can I assign different functions to the buttons (e.g. move the derailleur outboard with a left shifter click)?

Controller touchpoints are totally customizable to your preferences, allowing you to choose which paddle does what through the AXS™ app. Choose from three functions: Inboard shift. Outboard shift. Dropper. Yes, use one of the touchpoints to control your electronic Reverb AXS™ dropper seatpost.