I am using macOS 10.14 (Mojave) and just upgraded the MATLAB to R2018b yesterday and found a very strange problem. The editor runs EXTREMELY slow on my system and often freezes. When I click on somewhere on the editor or scrolling the view it usually takes 1-2 secs to response.
However, the strange point is, the problem only occurs when the MATLAB window is displayed on my external monitor. When I move the window to the macbook's internal monitor, everything is normal. And, the problem does not show on some specific files. I don't know if there are any features of those file, but if I make copies of those files, the problem may shows on the copies again.
I am not sure if it is a problem of MATLAB or my OS. How is the R2018b running on your systems?
There were instances of similar behavior in R2018b caused by the Magnet app. Turning it off should resolve the issue. Alternatively, you should be able to use keyboard shortcuts with no delays.
I've got the same problem. Matlab R2018b is very slow, but only when I'm editing scripts. It takes like a second for the courser so appear after I clicked at a point in the code. As far as I know, it occurs on the internal monitor, haven't tested a external one yet. The benchmark results are very bad, I'm always between 7th and 9th place, although it's a i7, 16gb ram macbook pro with iOS 10.13.
I have the exact same problem on my internal monitor, haven't tried with an external monitor. But the editor is very slow in Matlab R2018b, the cursor takes a couple of seconds to show up when I click somewhere in the code. Also when I want to run scripts I have to hover above the 1-2 seconds before I can click otherwise nothing happens when I click it.
Had the same problems both in macOS 10.13 and 10.14.
I have exactly the same problem on my MacBook. When I click on a line in a script it takes about a second cursor to appear, it's super annoying.