This is a very simple idea and should be very easy to implement :). Allow the double clicking of a folder in the bookmarks bar to have the same function as the "Open all" option at the bottom of the window that pops up after you click it only once.
I attached an image. Basically when double clicking the folder "example", Link1, Link2, Link3 and Link4 should all open up. I know the same can be achieved by just clicking the last button, but it'd be nice if the same could be done by just double-clicking.