I am unsure why this is, but after opening my project the day after, most of the custom classes with documentation in the Reference Documentation were gone. The ones that do show up have their custom icon missing and instead have a right arrow icon. I tried restarting the editor and launching my project, but nothing worked. How can this issue be resolved?

If you need more info, please let me know!
Thank you!

I forgot to mention that I am using GDScript and the new Godot 4 editor.

a month later

I was having this issue as well, my custom class wasn't showing in IDE class documentation. On a blank project (Then add custom class) it seems to work fine, but on my existing project there the custom class doesn't show.

The fix was to open the .gd file of that class, then cut everything under your class declaration
`class_name MyClass extends Node2D

...
`
Save it. Then paste back the code, resave it. This should force the documentation to refresh.