How do I change the default .ft file extension

FoldingText remembers that last file extension that you "Save As" as and uses that for future documents. So to change the default file extension you can:

  1. Create a new document and choose File > Save
  2. If needed click the disclosure arrow to see the full "Save As" file panel with all options.
  3. Uncheck "Hide extension" if it's checked.
  4. Type the filename (including a new file extension) that you want to use.