How do you actually change the project poster / thumbnail in DaVinci Resolve?

I cannot believe how incredibly difficult it is to change the poster or thumbnail for a project in DaVinci Resolve. This feels like madness.

I’ve tried every method I could find on YouTube and Google, and nothing seems to work consistently. Some people say to open the project, park the playhead on the frame you want, save, close the project, restart Resolve, and the thumbnail should update. Others suggest duplicating the project, changing the timeline frame, clearing cache, switching databases, exporting/importing the project, etc.

Still, the project poster either stays the same or updates randomly with no clear logic.

Maybe I’m missing something obvious, but for such a basic visual organization feature, this should not be this obscure.

Does anybody here know the actual reliable way to change the project poster / thumbnail in DaVinci Resolve?