Question:

How can a custom *.tiw file type be added to the Files of Type in the Import Survey Data command?

Answer:

1. Go to File > Import > Survey Data and change the Files of Type to "Text File (*.*)".  Select a file to import (any text file will work) and click "Import".
   
   
   
   
   
2. In the Text Import Wizard, Step 1 of 3, open the desired TIW and then "Save As" over the same file. 
   
   
   
   
   
   
   
   
   
3. Click "Yes" when asked to replace the existing file. 
   
   
   
   
4. You will then receive the option to "...add this format the the available File Types?"  Click Yes, and it will be added to the pulldown list.  You may then cancel out of the text import wizard.