One of the most missed features of legacy Final Cut Pro is persistent in and out marks. That is to say, once in and out marks are set in a clip, they remain exactly where they are, as a part of the clip, until explicitly changed or removed. Unfortunately, this arguably essential feature for digital video editing did not make it into Final Cut Pro X. If you set in and out points on a clip then deselect that clip and reselect it, the in and out marks are gone. While it is true that you can use ratings, like Favorites, in FCPX to create persistent clip selections, in and out points have valuable uses beyond just marking a usable portion of a video clip.