For the side wall mounting holes it is pretty simple, it just looks for the outline of the PCBA you are making an enclosure for, and then makes sets of holes spaced evenly, offset from the outline. I'm planning on making that a lot more customizable as well as have smarter defaults. Right now the hole placement does not take into account things like cutouts for connectors, which can be important.

The PCBA mounting holes are created based on the positions of drill holes in the IDF file, compared to a given hole size threshold that the user sets.