The change, if you’re interested, is in how the Design Screen works. Up till now, it has been running in IE11 mode. The updates we made in AppStudio 9.0.7 allowed us to use Edge as the engine for the Design Screen. We can get rid of a lot of code which was needed to stay compatible with IE11, but we want to make sure nothing breaks.
It turned out that this was a real problem, which did not have not an easy fix. The good news is that it is fixed now - and that there is a new beta to try.