What does the (outlined) asterisk after filename mean?

The little outlined asterisk on the right:

It means there’s an Annotation file connected to it.

This is covered in the built-in Help > Documentation > Appendix > Iconology.

Got it! Thanks!

I’ve noticed that if I delete all the text in the Annotation field, the icon doesn’t go away. I have to use the “Remove” command in the dropdown before it clears.

That’s because the Annotation file still exists. That’s not just a text field. It’s a view of another file existing in the database.