There is a way to activate reading mode when a class is called?
For ex. i have a file with a css class and i want every time i open that note to be in reading mode by default and when i open another note without any class to comeback to Editing mode
I think what you’re looking for is the Force note view mode plugin. This allows you to specify which mode a note is to be opened in, but using obsidian_ui_mode as a property, and I believe you also can set the default modes for those not having that property.