Not sure if this is occurred on every Mac systems, however I have been experiencing on every Mac (3 MacBook Pros) I have been using.
I have been using UE4 on Mac since 4.17 and when I was navigating buttons in umg, it has always caused lag between navigating buttons. For instance, just navigating the button through the arrow keys or using gamepad caused the lag and sometimes just right clicking also caused this issue.
Least I know is that my system is not a reason because my Mac has Intel i9 (9880H) with Radeon pro Vega 20, with 16gb ram. I also tried the same project via bootcamp and there was no issue.
In addition, as far as I have experienced, this issue only caused when I was playing in unreal editor. Compiling and packaged didn’t caused the problem.
Is there a specific reason why Mac version of the UE4 has a lag on ui navigation? If so, what is the solution?