A key feature of the original Macintosh operating system was an orthogonal interface for copying, pasting, dragging and dropping arbitrary data, whether plain or styled text or graphics, into (more or less) arbitrary locations, which was far from obvious in consumer systems of the time.

And when QuickTime came about, video was no exception. You'd select a length of video from the timeline, copy it and either paste it into a different video, or into a presentation or other kind of document. It's ridiculous to call the ability to use the OS the way it was intended a "pro feature" that you should have to pay extra for.

You could select sections of video and copy/paste them. QT Pro was a lightweight video editor and encoder.