Class not displayed

Why is the class not displayed?

It’s a private class used to style the default class clean option in Blocs. Did you input that class name?

I have inserted the class with the Classmanager - Subclass Lip - Buttons - Button clean.

But I found today that it is obviously related to the backflash. If the text does not contain a backslash, the class appears at the top right. If it has a backslash, the class disappears at the top right.