I was clicking lots of buttons in the toolbar to try to hide things I didn’t need (browser, inspector, etc.: I wanted the preview window as large as possible to get more detail in a crop) but the timeline disappeared too.
I thought “great that means the preview window can be even bigger”.
But now I can’t get the timeline back.
In fact, both the browser and the timeline toolbar buttons are greyed-out:
How do I show the timeline again?