How can i add a customizable bar (as the top bar) from at my GP child theme?

Link of image: https://adobe.ly/38QqfS1

Hi there,

For that spot, you can either use a header element:
https://docs.generatepress.com/article/header-element-overview/

Or after_header hook in hooks element as shown in your screenshot:
https://docs.generatepress.com/article/hooks-element-overview/

Let me know if this helps :)

Thanks! Leo.

No problem :)