Is it possible to add a promotional banner /alert/balloon like comment under category on portal

[Priya16xv]

I want to add a banner or clickable link on the portal under any specific category, is it possible? if yes how we can achieve this.

[Mark Manders]

What to you mean by 'category'? 

[Priya16xv]

I want add text or clickable link at the green highlighted area.