Ctrl-T opens a new, blank tab at the end of my tab list, which I like. In IE 11 middle-clicking on a link in a web page opens that new progeny tab next to the parent tab, rather than at the end of the list, and groups them if you have more than one parent-and-progeny tab groups. IE 11 goes so far as to assign tab title background colors to such groups (which isn't as important to me as the functionality). Tweaking Tab Mix Plus just resulted in modifying where Ctrl-T puts a blank tab. Is there a way to make my FF parent-progeny tabs work like IE 11?