In CAM after postprocessing a file we are presented with a Save dialogue of the form
filename.nc
filename.cnc
(extension depending upon post processor).
Today the whole text string is highlighted which means that, if you start typing in order to name the file you're going to have to retype the file extension.
Alternatively you could look for the mouse and select just the filename (that's what I do).
Both are slow.
Suggestion: when the file save dialogue comes up, highlight only "filename" and not "filename.cnc".