You can modify the placement by changing the add_toggle_link function. In there you see this call:

var tbl  = document.getElementById('titlebar-bottom');
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What it's doing is finding the element to place the toggle link after; in this case the element's id is "titlebar-bottom." One easy way is to always have a certain nodelet on top; in my case that is the XP Nodelet. Then you could change that search to:

var tbl  = document.getElementById('XP_Nodelet');
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And put the link before, instead of after the one it finds.