In comparing the experience between commercial and GovCloud (US-West), the “Topics” tab is not available in GovCloud (US-West). When following the doc to create a Topic it is therefore not possible in GovCloud: Creating Quick Sight Topics - Creating Quick Sight Topics - Amazon Quick
That is definitely some interesting behavior you are encountering. I have not seen any documentation as well that mentions Topics exclusion, and the fact that you are able to still create Topics via the CLI means this very well could be a bug within the UI for that region.
I will make sure to mark this post as an error to promote further awareness to the AWS Team. In the meantime, I would definitely recommend creating a support ticket with AWS Support, as they will be able to confirm if this is indeed true and better assist you from there.
Just checking back in to see if you viewed my previous post in regard to creating a support ticket. Please help the community by marking this answer as “Solution” or following up in general within the next 3 business days!
The Amazon Quick team has confirmed, Topics isn’t Generally Available (GA) in the GovCloud region yet. Although they are currently working on expanding to the region, a definite target date is not established as to when it will be available in that region.