1. Navigate to the Surfer installation folder (by default this is C:\Program Files\Golden Software\Surfer\). Select the Gsio.ini file, press CTRL+C to copy the file, and then press CTRL+V to paste a copy into the same directory.
2. Open a text editor program like Notepad as administrator.
3. Click File | Open.
4. Select All Files (*.*) from the file type list.
5. Navigate to the Surfer installation folder and select the Gsio.ini file.
6. Click Open.
7. At the bottom of the file, under [ExportFilters], highlight the file format you want to be first, and press CTRL+X to cut it.
8. Remove the empty line.
9. Click before the first file format and press ENTER to add a new empty line at the beginning of the file formats list.
10. Click in that empty line and press CTRL+V to paste the cut file format to the top of the list.
11. Copy steps 7-10 as desired to rearrange the file format order (you don't have to add the empty line at the beginning of the list in step 9).
    * Be sure not to remove or duplicate any information.

[ExportFilters]
dxf = "DXF AutoCAD DXF Drawing", ioDxf, ExportDXF, 3S, *.dxf
adf = "ADF Arc/Info Binary Grid", ioAdf, ExportADF, U, *.adf
am = "AM Amira Mesh", ioAmira, ExportAMIRA, URC, *.am *.col
....

Updated October, 2021