I wanted this Thunderbird add-on so that I could enlarge the font size in the toolbars and side panel. It does that nicely.
Unfortunately, it also cuts off the bottom of many dropdown menus. For example, I find that enlarging the above fonts by 120% works well for me. But, if I want to “Import” a file, this add-on cuts off the bottom of the action window. So, one can’t see the “Next” button to continue. You’re frozen there and have to restart Thunderbird to undo the damage.