I'm working on a brand new 2018 rMBP with 32Gb of memory and the IDE is painfully slow. It takes several seconds to draw controls on the windows, etc.
Please do a search on this forum for threads named like yours.
There is a problem with Mojave and GroupBoxes currently, but in some cases there seem to be different causes for IDE slowdowns on a Mac which usually was the fastest IDE platform.
Thanks for the suggestions! I will try using Windows 10, but the main reason for us to go with Xojo was to get away from Windows.
I did do a search on the topic before posting and it seemed that many of the issues were with other versions. That is why I started one with 2018r4. Again, thanks for the help!
Hope we can resolve this issue.