µBlock (uBlock) provides action operator :remove-class(), but how can I add a CSS-class?
On a site an element alternates between two CSS-classes. I have a rule with :remove-class() that is triggered every now and then, but then the page looks weird. Therefore, I want to remove one class as I do now, but also add the other CSS-class.
example.com##.ad_wrapper:watch-attr(class):remove-class(ad_wrapper-visible)!how to add class "ad_wrapper-hidden"?