Make a second version of a video
Keep a clip two ways — the whole thing and a short cut of the best moment: Duplicate for editing makes a second version to trim, grade and convert.
Making one
Select one or more videos, right-click and choose Duplicate for editing (or Duplicate N videos for editing). Each gets a new library item beside it, named like clip (2).mp4.
The copy is a real file, because a video cannot be played without one, so making it can take a while for a long clip on a network share. Its progress, with Stop, is under Thumbnails & video, and the menu row is greyed out until it finishes.
How the two versions relate
Both versions render from the same kept original. So each one is only ever one step from the camera's file, however many times either is trimmed or graded.
For photos, the equivalent is a virtual copy, which needs no second file at all.