Seeing source material in the Timeline Window

By default, the Timeline Window displays the sequence that's loaded in Record Window. However, it's possible to have the Timeline Window display what's loaded in the Source Window. Being able to do this is useful when you have loaded a sequence into the Source Window (when you're editing a portion of one sequence into another) and need to see the transitions, or when you want to see the audio waveform for what's loaded in the Source Window.

To do this, you use the Toggle Source/Record in Timeline function, which is found by default in the bottom left-hand side of the Timeline Window next to the Video Quality Menu. It's an icon that resembles the Source and Record Windows, where one window of the icon is dark and the other is light, as shown in the following screenshot:

When you click on it to enable it, the button will turn green. You'll also see that the Position Indicator line in the Timeline window turns green to remind you that you're looking...