The scrollbar cannot be moved out of its current position. It can only be resized. Should be able to apply 'position' CSS to scroll bar.
Thank you for the report! Could you please attach a test case, ideally one that works as expected in other browsers?
This would need to be specified by the CSS specs, and would require support from other browser vendors. There would be a pretty high bar to change this.
<rdar://problem/94356950>