The sidebar is a list that show your recent activities within Tamago-DB. 

To show the side bar, click on the gray tool "splitterappearing on the edge of page. 

You can favorite your activity by hovering over the space left of the activity title, a heart icon will appear, click the icon to add to the favorite list.

The favorite activity will show on top, even if you clear the activity history, the favorite activity will remain available.

To remove the item from your favorite list, click on the [heart icon] of the favorite item.

If the sidebar is taking up too much space, you can hide it to increase the amount of space available in the main content panel.  Simply click on the "splitter" to hide the sidebar.