Yes, you can sand the calcium silicate boards to be able to work with them in hard-to-reach areas, for example. You can simply sand the calcium silicate boards by hand or with a machine using sandpaper, but sanding with a fine rasp would also be an option.
The hinges of window reveals are often somewhat more difficult to work with, meaning that the windows can no longer be opened when using calcium silicate panels. However, so that you do not have to do without calcium silicate boards in window reveals, you can grind the boards to size in the relevant places so that the window can still be opened without any problems.