[Zubersoft]

If you assign a tool to the two finger tap in the annotations editor, the two finger tap switches between your current tool and that tool. So if you set the two finger tap to the "Pan" tool, then you can switch between the pen and that, or the highlighter and that. So given your example, the current functionality already works. Switching between any of the last two tools is maybe useful in limited scenarios, but I actually struggle to think of times where you'd always want it to be between two random tools, instead of the current tool and a designated tool (like the panning tool).

Mike