You can now "favorite" any post (video, pictures, write ups, or news like this) by clicking the favorite button just below the post. This will then save itself on your Favorites List on your account.
You can access this list from the top menu under My Account > My Favorites, or from the side bar menu below your profile image (on mobiles, the side bar is at the bottom of the page).
You can remove favorites by clicking the same favorite button to "unfavorite" it, which can be done from the post page of from your favorites list.
This should make your life a whole lot easier to collect all your favorite videos.