Browse and Edit works only for pages. Adding content items should be done from the backend >> Content modules. Browse and Edit allows you to modify the page data - controls and their position on the page.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items