Scaling -> Restore default... Scaled everything to tiny elements.
On FP2 this action set value to 13. After UBports install the scaling was set to 23, I believe.
So, "Restore default..." made all elements tiny, with respect to the previously configured value. And there was no chance to preview effect of the setting before activating it. At the end, I had somewhat hard time changing it back.
FP2 / Ubports rc 2019-W24
UT Tweak Tool 0.4.15