I would also like to show you our Experimental Feature - Analytics Catalog: The Analytics Catalog lets you search through and access all your visualizations, dashboards, metrics from one place, mitigating some of the bloat that comes as the size of your project grows. You can find it on the Home page.
However, at this time there is no way to delete visualizations there - So I am also going to highlight this there, as I think would be an ideal solution 🤞
https://www.gooddata.com/docs/cloud/experimental-features/analytics-homepage/