Seems superb to me. I bookmark A LOT. (What can I say: I'm a curious guy.)

Anyway, this allows you to add "his bookmark" (including the location where bookmarks will be placed, and much more) ... AND ... control the behavior of the Firefox bookmarking tool (including location, etc.)

In short, it's simple, quick, easy, intuitive.

(I just thought of this: I suppose if one wanted TWO defaults, this would let you set Firefox as #1 default location and Teddy's as default location #2. Easy/breezy.)