To add a new extension to the system, click on the button at the bottom-right corner of the panel, as shown below:

A new window will open. Enter the extension number and click on the button. If the extension number exists already in the system, you will be prompted in order to avoid creating duplications.

After clicking on the button, the window will appear, allowing you to configure the properties of the new extension.

Enter the required details and click on the button to apply the changes.

The new extensions you have added will be displayed in the panel, as shown below: