I'd like to have all tabs of a single website grouped into a parent tab, so that they have a hierarchical structure. Graphically, just a drop down would be good. Does it exist? I use Safari on OS X Lion.
You can group multiple tabs in new Safari windows:
You can actually drag tabs from one Safari window into another Safari window (into the "tab" area of the window).
(I can do this on OSX 10.4 Tiger)