Cannot Disable Highlighting Effect in Composition Mode

Somehow I turned on a permanent text highlight in the Composition Mode and now I cannot get rid of it. Looked through the manual but I am not sure what to call this feature. Selecting and deselecting has no affect on the effect.

I opened another project, entered Composition Mode and found that the effect was not there. While in that project I saved its Composition Mode settings as a preset and returned to the original project.

In the original project I selected that preset. It did change the other, overall settings but had no affect the highlight. I am assuming that this feature is not part of the composition mode but is set outside of the view.

New paragraphs and different chapters have show same effect. This effect is only evident in the Composition Mode and not in any other editor view.

What is the name of this feature and how do I turn it off?

Thank you

There is a screenshot of the feature attached to this post.

Latest version of Mac OS Mojave, latest Scrivener version on MacBook Pro