Hi Daniel, There is no list available regarding css class names. But you can find available css class names using the below link
There’s some documentation on Atlas UI (which is used by projects made in ‘recent’ versions of mendix) on this site: https://atlas.mendix.com/
But I don’t think everything is on there (neither is it in list form)
As Atlas UI (and the previous styling) are based on Bootstrap 3 you could also check out the documentation for that. https://bootstrapdocs.com/v3.0.3/docs/css/
Not in Mendix Studio Pro (aka the Modeler), but you can check the css-files in the directory project-directory/theme/style/css/:
- custom/custom.css and
Mendix seems to have Mendix Studio (the webmodeler) as a new editor, but also that one does not have any information on the available classes. Maybe add an idea?