HI Dougie
You can store the virtualdub filters .vdf files in their own folder within the NCH folder. (Anywhere actually)
As they are additional filters they won't appear under the "Effects" tab as such but at the same time you only need to load them once when you want to use them.
Starting from scratch....
Go to the virtual dub filter page and download a filter you require. Save it to your prepared folder.
Put your clip on the sequence line and activate it.
Left click the "Effects" button (Film frame with yellow star) This opens the video effects window.
To the right of the top "Auto levels" box click the little down arrow.At the bottom of the list that appears is "Load/Unload Virtual dub plugins" Select this option. This opens the active Virtual dub filter list (which may be empty if you have never loaded any)
Click "Load",; navigate to your prepared filter folder and load the .vdf filter you want.. It will now appear in the window (or be added to list.)
When you now want to load that filter in the future, Activate the clip then click the "Effects" button and then the down arrow (as outlined above)
At the bottom of the list will now appear any filters you have added. Just select it......
Until you remove them from the list (or change their location) they are always available.
Nat