I can’t get this pane to enlarge.
I wanted to fix this and first opening the export panel I saw the exact same thing as you. Then I started debugging and it fixed itself and now I can’t reproduce it any more. What happens when you switch to the “Metrics” and back to “UFO”?
Edit: I found the problem. It happens when you first export a font with one master and then one with more than one. I fixed it.