Like some others on the forum, I have searched for a way to display the Cap Height everywhere because I find it easier to have every visual guides at all times.
I opted for the “Scope” solution which works well for designing, but I just realized that this sets Cap Height to 0 on my OTF exports. I duplicated the file and removed the Scope setting: everything went back to normal. Just wanted to let you know.
I know this and this is why you should not add a scope to the default metrics.