Thanks. Rated 5 out of 5 stars

But the following CSS-Code does roughly the same:
#personal-bookmarks {margin-right:-60px !important;}

Wouldn't that just remove a fixed amount of space from it? No good if you don't have your browser window the same size all the time.

Part of the problem is the bookmarks bar/items are set to span the full width, so if they're on the same row as something else that does the same (like the tab strip or the address field), they each get 50% of the width, with the bookmarks' 50% being mostly wasted space if you only had a few icons in it.

Changing the flex attribute via XUL stops that from happening. I could not find a way to do that using just CSS which is why I wrote the extension.