On TikTok, you can you use the Favorites feature to save a video you like so that you can easily find it later.
How to add a TikTok video to Favorites
To add to your Favorites list a video on TikTok you can use the bookmark icon that you see on the right side of every clip.
Keep in mind that the creator can see the people that saves their videos.
Where to find your Favorites
To see the videos you saved to your Favorites, go to your own TikTok profile. There, on top of your own videos, you can see a row of buttons.
The third button in that row has the same bookmark icon. Tap that and go the videos subsection, which is also the first Favorites subsection.
This way, besides videos, you can save other things on TikTok, like sounds and effects.