How do I increase the size of the preview pane when I mouseover threads in firefox?
I use the “Popup Alt Attributes” extension XUL Apps > Popup ALT Attributes - outsider reflex
The popup disappears in a few seconds, so you have to move the cursor away from the area then back to see it again.
It’s a little buggy. Sometimes it won’t display the popup at all. But it’s better than the limited amount you see otherwise.