Try the demo

1. Enable Internet Browser UMG in Plugins.
2. Enable Show Plugin Content.
3. Open InternetBrowserUMG/DemoLevel.
4. Press Play — use tabs, address bar, and bookmarks.

sequenceDiagram
  participant User
  participant Shell as WBP_InternetBrowser
  participant Tab as WBP_InternetBrowserContent
  participant IB as UInternetBrowser
  User->>Shell: Switch tab / new tab
  Shell->>Tab: SwitchTab
  User->>Tab: Enter URL
  Tab->>IB: LoadURL
  IB-->>Tab: On Load Completed

Inspect Initial URL and whitelist settings on the embedded browser widget, then compare with the Widget reference.