I've been seeing this appear alot in discussion and I thought I'd share this short guide into enabling animated previews. Wan is very capable but not every generation will be gold, and it stinks waiting 5 minutes only for it to turn out poor!
This is what you need:
https://github.com/Kosinkadink/ComfyUI-VideoHelperSuite
Then, Go
Should get you all set! (sorry the webp is so low quality, though the preview still won't be 1:1, for sanity's sake.)
In the example below, you can see it's still an early step, so the preview is quite noisy still but will clean up as it gets more steps in. You can usually tell at about 20-50% if it's not going to get any better.
EDIT: If you copy those settings from my sampler the riflex_freq_index is experimental and I don't recommend using it at this time, but the other settings I like but to each their own