Which of the following actions can NOT be performed in the Timeline?

Loading clips into the Source Monitor is not considered an action that can be performed directly on the Timeline. The Timeline is primarily focused on the arrangement and sequencing of video and audio clips, as well as applying effects and transitions.

In contrast, mixing soundtracks, adding titles and graphics, and making editorial changes to clips are all core functionalities available within the Timeline environment. When you mix soundtracks in the Timeline, you can adjust the levels, apply effects, and create a cohesive audio experience that aligns with the video content. Similarly, adding titles and graphics allows you to layer text and images directly onto your video timeline, enhancing your visual narrative.

Making editorial changes, such as trimming, splitting, or moving clips, is fundamental to the editing process and is a primary function of working within the Timeline. Each of these capabilities directly involves manipulating the visual and audio aspects of your project right where they will appear, while the Source Monitor serves a different purpose, providing a separate interface for preparing clips before adding them to the Timeline.