I looked in the docs and google but could not find the answer.
Can diffuse do 3-way merge in which it gets the 4 files? and display it in three panes (the output pane across the bottom)?
Currently there is no explicit merge pane at the bottom but this feature is high on our to-do list. Right now, Diffuse treats all panes as equal peers. Usually the second pane is were merging work is performed.