In the design section, a 3rd tab from the right is named as the components tab. You have used it to select the components which were added on to the Screen, to further edit their properties. But, have you ever thought why is it needed if we can select the component right in the viewer. Here are the three main reasons of why you need a components tab:

1. Components tree:
It describes the sequence of different components in the Screen in the most desirable format. For one it may seem that yaa! I can observe it directly in the viewer. But, let me remind you that all the components may not be necessarily visible on the Screen.
It is helpful while adjusting the position of a component. The components tree starts from the name of the screen1. Each new Screen has a different components tree.
2. Naming the components:
In the components tab, we can give each component our own name; For example, add for Button1 (when you want to perform addition operation).
Renaming a component is very helpful especially while working in the blocks section because every block that you use will have a proper meaning. Ex. When the add button clicked, set the count text to count text + 1

3. Deleting the components:
To delete any components you need to select the component and then, click the delete button available in this tab. It asks a confirmation message before you are going to delete the app.