What action is represented by the key 'Z' in a timeline?

The key 'Z' in a timeline is often associated with the action of maintaining the rhythm of a sequence. This can refer to creating a sense of flow and pacing within a project. When editing video or audio, it's crucial to ensure that the cuts and transitions contribute to a cohesive storytelling experience. The action represented by 'Z' typically reflects the editor's ability to keep the timing and rhythm aligned with the desired narrative or emotional impact, making it an essential tool in the editing process.

The other options pertain to different editing functions which do not align with the specific purpose of the 'Z' key. Selecting a whole clip, for example, deals more with clip management rather than rhythm. Removing material without closing the gap focuses on altering timelines without affecting surrounding content. Displaying waveforms is related to visual representation of audio but does not directly involve rhythm maintenance. Therefore, the representation of the 'Z' key as maintaining rhythm fits within the foundational editing principles necessary for effective storytelling.