Procedure

For this example, we use a Gain as the control track object.

1. Add a Timeline component to your design.
2. Add a Gain component to your design. Wire it to output 1 for the purposes of this exercise. You can rename the Gain component if you wish or use the default name. 
3. Pull any controls from the Gain into the Named Controls section of the Design Elements pane. You can rename the controls if you wish or use the default names.
4. Save and Run the design to the Core and open the Timeline component. 
5. At the top right of the screen, there is a square button that has circle and a plus symbol in it. If you hover over the button, it says "add control track". Add one. (You can add more if needed.)
6. Once the control track is added, there is a drop-down menu in the controls track settings area to the left of the settings. Select the Gain control.
7. Once the Gain control is selected, you can add a marker to the track. Drag it around until you get the level you want. 
8. Drop another marker at the 1 minute mark. Drag it all the way to the bottom off the track, without removing it.
9. Press the Play button in the top left transport control window. The play head will start to move as the time counts up. Notice the level on the Gain is going down slowly over the minute.