Add Fishbone/Ishikawa layout
I think it is very self-explanatory. The current layouts are basically "expand-out" formats. The Fishbone/Ishikawa keeps the name for the branch at the end of the branch and new banches build within the domain of the branch.
It would be nice if hovering over the branch label would bring-up a pop-up window with the summary/description text... something useful to navigate the diagram, see what is missing and what has been checked out.
Ismael Torres commented
Here are a good number of examples of the fishbone diagram: http://unmasadalha.blogspot.com/2016/01/fishbone-diagram.html
These are very useful for problem solving!