You can open the reference browser in a new window by undocking it. This is useful if you have a lot of screen space (such as a 4k screen) and don't want the browser to clutter the workspace.
With the reference browser open, click the Undock button in the top left corner.
This creates a new window for the reference browser.
To redock, click the Dock icon on the top left of the browser.
Hre is how docking and undocking the Reference Browser looks like: