Thank you Klara for taking the time to provide a detailed reply. I'm assuming your answer applies to ArcGIS Enterprise Sites as well.
I understand, given the complexity of Sites, that we should not be editing the CSS pages. And though gimmicky, the trick about using spacer cards might be a work around.
I've seen the "Row Settings > Appearance > Row CSS Class" and I get the concept from 10,000 feet but am not quite clear on how to put it into practice. I can't seem to find any examples of this through Google (if I use quotes in my search, I keep landing on this page). I get that I'm to reference a CSS class but I don't know what name to use or where to put my own custom class so I can create properties for it and then reference it.
In the likely event that others will land on this page with the same question, do you mind taking a minute to provide a simple snippet showing how to put Row CSS Class into practice? Or maybe just reference a helpful doc for us (again I'm using Enterprise Sites)? Thank you.