The icon with the clock is the Time Slider feature.
Clicking on the icon enables the feature and presents a chronological time lapse of all the absent elements in the order that their corresponding plays were written.
Once enabled, you can pause and play with the slider in various ways.
Drag the mouse to the little box with the time frame. Hovering over it will display the slider as well as buttons to pause and play, fast-forward and rewind, and alter the speed of the time lapse.
The default time frame is one year. Thus all elements from plays written within every year are displayed at a time.
To change the time frame, drag either end or both ends of the slider to your desired time frame. For example, a time frame of two years will display all elements from plays written within two years at a time.
The pause and play, fast-forward, and rewind buttons perform the functions you would expect them to.
By default, the time-lapse speed is set at 1x. You have options to increase or decrease this speed within the time slider box.
To close the Time Slider feature, click on the X of the box or on the icon with the clock.