Rephrased: Exclude all files in a directory, except one (or more) specific file(s).

Following is an example of how to exclude all files in "C:\Test\", except the file "C:\Test\keep-me.txt".

1. The directory "C:\Test\" must be selected (yellow checkbox).

   Unselected directories will be ignored throughout the rest of the filter process.

2. Right-click any file in the Files panel: A popup-menu appears.

3. Select 'Exclude/All Files in This Dir'.
   At this point all files in the directory "C:\Test\" are excluded.

4. Next, right-click the file you want to include ("C:\Test\keep-me.txt"), and choose 'Include (Always)/This File'.

5. That's it!
   At this point all files in the directory "C:\Test\" are excluded except for "keep-me.txt".
   You can repeat step 2 for other files you want to force-include.