Maybe I should file a bug report on this, but it’s a nice example of lack of usability due to colliding needs: the need for a scrollbar in the terminal, and the need for window resizing.
As you can see, the popup scrollbar always follows the mouse pointer, making it impossible to get the resize operation. This happens in the bottom-right corner as well. The only way to perform resizing is to either use the top right corner, or to “trick” the scrollbar by moving the mouse pointer in a particular way, something made even more difficult by the fact that this area is one or two pixels wide.
This is so wrong from the usability point of view that I am surprised nobody caught it.