R
@Pesala Yes, dropping the link on the tab of the tile is the only way to do this
However, as a user of the really old Firefox (pre-57) TileTabs, I really love the ability to just drop the link anywhere in the page to be replaced. It is VERY much faster than finding the tab for the tile, especially as I prefer to use CLOSED accordion tabs at all times.
Regarding super-drag-n-drop, I think I voted for that one too, but that request has a ton of features that are just not part of my workflow, nor is this request an explicit part of it. I will re-read it to be sure. (Update: that one is all about opening stuff in new panes. Not at all like this one)
This one is clean and simple: (Note also, this is FireFox's normal behavior)
If a user drops a link (or shortcut) anywhere in a pane, then load the link in the pane that got the drop. Done.