In case it isn't self evident (wasn't to me); when grouping your book marks into folders check the box to the right of the bookmards/folders and they open as tabs all at once. Very handy when you use certain bookmarks all of the time.
Click on the bookmarks icon on the left of the bookmarks bar. Click on the "bookmarks bar" menu item on the left. Now, once you make a folder and group bookmarks in it, the above mentioned check box appears to the right of the folder.