I'm trying to customize the header of my ArcGIS Hub for COVID-19 by using the 'Custom HTML/CSS' option. After expanding the editor and making changes, the 'Apply' button fails to activate, leaving me unable to apply my changes. Curiously, selecting all CSS text and deleting it seems to be the only thing that activates the 'Apply' button.The problem is I don't want to delete all of the header CSS, only slightly modify it! Am I overlooking something obvious?