[x] choosing the q for plots: for experimentalists is common to do not have the Gamma in the iBZ, but in outer zones. So, it can be useful to define the path by hands, like: (0,0,2) -> (0,0,3) .... and so on. Similar to what is done in bands but with vectors, not letters.
[x] Constant energy slice plots: plot the S(q,w) in a particular plane in the 3d q space. definition of the plane (3 q points) and of a maximum q distance. Or, define 4 points to detect a square. Definition of a mesh grid.
To have examples on the output plots: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.106.224304