To modify default settings for the XISF format:
- Open the Format Explorer window. If it isn't already docked on the left side, select View > Explorer Windows > Format Explorer from the main menu.
- Activate (e.g., double click) the XISF item on the left panel.
- On the XISF Format Preferences window, change settings as desired; then click OK.
Note that the same can be done for any format support module that provides a preferences interface. This currently includes XISF, TIFF, RAW, JPEG, JPC, JP2, and FITS.