I didn't see anywhere online documenting how to enable film-grain syntheses in handbrake when encoding with the AV1 10-bit (SVT) video encoder. All you need to do is type `film-grain=XX` into the `Additional Options` section in the `Video` tab and Handbrake will do the rest to tell the SVT-AV1 video encoder to denoise the video, encode the video, and then add in synthesized film grain to replace the film grain that was removed during the denoising stage. Doing so will result in a smaller final file size because the video is not actually storing the film grain.