When selecting an icon using the Visual editor, it creates it normally, but does not properly format it so the icon can so up on index pages. for example: when selecting the banana icon in the visual, the icon field is filled out to be "fa-banana" when it should be, "fas fa-banana"
Create new generic article.
Select an icon by clicking on it. (Banana in this case)
Give article name.
Set parent for article (I used gamemaster vault)
Publish article
select "view in world"
scroll to bottom of new article and select "gamemaster vault" link
Notice that article does not have icon in "World Codex" index.