You can only do that by creating a bookmark on the Bookmarks Toolbar with such a single link.

That doesn't open a window with a single location. It simply opens the site for that bookmark "in place " at the current tab.

Press the Shift key and left-click if you want to open a link in a new window or Ctrl to open in a new tab.

I guess I'm not explaining myself fully. I have a home page designation in firefox preferences that starts firefox up with 5 sites. that pretty fills up my screen with tabs. At some point I want to initiate another WINDOW in firefox (NOT a tab). I would like to be able to open up a window that ONLY has ONE tab, or as if there were only one site designated as the home page. This gives me a workspace that has my most useful sites available in tabs in one window, and also another WINDOW that I can move around in and even create more tabs without messing up my primary set of TABS (in my primary window). I see how this might not be doable without doing what I do now, which is open up a new window, and then close tabs until the new window just has one tab for me to work from.

Firefox always opens a new window with the home page(s), so you need to use Shift + left-click on a link (bookmark) to open a single page in a new window or simply tear off an existing tab by dragging the tab slightly down to open the tab in a new window.

Shift left-click is the ticket....!

Thanks....