"Export to PcbNew" could work out layers for you

Could the layers to "export to" be inferred?

Should I be able to export the "drills", or are drill files inferred? (I ask because drill file is included in the dialog, but there seems to be no appropriate layer, and I guess the drills are implicit in the pad definitions anyway).

Also - I initially tested this feature using files simply entitled 'bl' 'bo' 'bs' etc - no extension. When I press "store choice" for one file name convention, hopefully that does not affect other file convention associations? Is there something like an INI file where for instance we have, for Bottom Solder mask
.gbs=22
...
bs=22
...