I have been having the same problem as everyone above. Was working fine on my old Mac Air with 2017 but as soon as I moved to my new Mac pro and InDesign CC 2018 it hasn't worked. Everything is slow and there is a beach ball every 30 seconds to a minute.
I have followed these steps and this hasn't changed anything. This is very annoying as I am trying to complete exams with strict deadlines and this is piling on a heap of pressure.
I was able to change these:
But when I tried to add an account on these three:
I didn't have permission. I went onto the root account and still didn't have the permission to complete the task. My indesign is still terribly slow so please can someone fix this. It is costing me a lot of money for pretty much nothing.
Sorry for the inconvenience caused. As you have already tried sharing permissions from root account and it's not letting you add your account. Could you please confirm how was the performance in root account?
Also, please try resetting preferences for InDesign