This is a premium feature available with the Astra Pro Addon plugin. To use these Pro features, you need to have the Astra theme along with the Astra Pro Addon installed on your website.
Header Sections module introduces two header sections (Above Header and Below Header ) in the website header.
You would not find the Above Header/Below Header Section separately if you are above the Astra version 3.0.0. You will need to visit the Header Builder section and edit the insert elements to the first and last row virtually. Learn more here.
You can find settings under Appearance > Customize > Header
Explore the settings for Header Sections in detail –