An extension to get you started with managing several websites.
Ultimate Webmaster is currently "bookmarks on steroids". It lets you open a Group and / or a Set of Pages at the click of a button.
Groups will open a list of URLs in a click.
Page sets let you open a set of pages based on a list of "roots" with just one click. For example, if you configure 2 roots:
Then you can have a single button to open: