In 4.0+, dragging with the right mouse button will pan the dopesheet either up/down or left/right. This doesn't work for the tree and other scrollable areas, but it should
we'll make it happen.
We'll also make the U
and J
hotkeys work for scrollable areas. Until then there's not a great way to zoom the timeline/dopesheet using a pen. You could click/drag the slider at the bottom left of the dopesheet view, but I know this can be sensitive. Otherwise the next best thing would probably be to hover the timeline and use the mouse wheel.
In the graph view U
and J
work like the viewport. Also note you can zoom the graph by holding alt
and dragging with the right mouse button.