Right now, in order to use biblatex fields rather than the native bibtex fields, it seems necessary to download the file TypeInfo_biblatex.plist, rename ~/Llibrary/Application Support/BibDesk/Typeinfo.plist to something else, put a copy of TypeInfo_biblatex.plist there, and rename it TypeInfo.plist (and similarly to reverse the process). It would be so much easier if there were just a switch, either on the main menu or in Preferences, to switch between the two modes. (JabRef has this.)
Does Typeinfo_biblatex really reflect the biblatex fields? As I understand
it the set of biblatex fields is unwieldily, and this is just a subset. I
am not sure we should try to support some default that is in some sense
arbitrary.
I am unsure how to combine such a choice with our ability to modify the
fields.
Perhaps we could add an ability to save a particular customization under a
chosen name, and then allow to select, from a pop-up, a saved set to revert
to.
It's been a long time since I looked at the biblatex manual, but IIRC it changes the semantics of a couple of existing fields, so long-term compatibility seems dangerous. https://tex.stackexchange.com/a/37133/61839