I found this tricky at first. This is how I do it (although it can also be done with a terminal script if you're up to it):
Open Finder > Macintosh HD> Users> Josef
then Cmd+Shift+. reveals all hidden files/folders
click on .config>Darktable and all your hidden DT files will be there.
Cmd+Shift+. closes all the hidden files when you've finished.
Following Steve's earlier advice I keep recent copies of these files so that they can be used to restore DT if I do anything silly. Good advice, I think.