Which action can be taken to view audio waveforms within the timeline?

Using the Toggle Source/Record button in the timeline provides the necessary functionality to view audio waveforms. This action allows you to switch between different views so that you can see the audio information represented visually in the timeline. This is crucial for editing purposes, as it lets you see the amplitude and patterns within the audio, enabling precise edits, adjustments and ensuring that the audio aligns well with other elements in the project.

The other options do not facilitate the viewing of audio waveforms. Clicking on the timeline's play button merely plays the audio without providing any visual representation of the waveforms. Importing audio files relates to getting audio into the project but does not affect the visualization of the waveforms in the timeline. Adjusting audio levels in the mixer focuses on managing audio output rather than displaying waveforms, which is essential for visual editing tasks. Thus, the Toggle Source/Record button is specifically designed to enhance the editing workflow by allowing for the visualization of audio waveforms in the timeline.