Hi there,
So I don’t know how about you, but I usually spend a couple of hours reading the chapter to find the little mistakes (speech bubbles, spotting, grammar mistakes and so on). Usually I do it without an access to the web portal, so I can’t improve it immediately.
Maybe it’s just my case that I see thousands of little things that I would like to improve but I don’t remember all of them later, when I’m working on the story. So I guess I need to read it like twice as much just because I missed something I already knew was there.
I would love to have something like mark tool on the app preview where I can just click the button in a random place.
And when I’m going on a web portal I see in the script marks next to the marked line. Something like this:
It can be temporary, marks can be cleared after saving the story. Or there could be a list on the left with marks and “clear all” button, but I think it could be too advanced.
PS: It opens the gate to mark mistakes by other people. Sometimes I see in stories mistakes in layering or some little mistakes and I think an authors would be happy if little misakes were mentioned to them by readers or testers. But it’s the different topic 
but maybe I’m wrong 🤷