I couldn't find it but as far as I remember, I did request this feature in the past. Maybe I did mention it in a comment on another topic. Ash did mention that the article unpublishing feature is going to be released in Q1 2021 in this topic "How to unpublish or move Knowledge Base article to draft".

I also want to present the idea of "deprecation" and "obsolescence". Deprecation / Obsolescence

Some technical bulletins, how-tos and service instructions do become either deprecated or obsolete in time and in such cases, we need to inform our registered users about them. These articles should also be tagged as such in the KB and be displayed differently at least with some visual guidance. People should immediately be made aware of the special status of them. We should also link them to the superseding articles if they do exist.

Please share the work that's going on with your development projects so we could interfere with our ideas in case we want to, before some new feature is released without fulfilling everyone's requirements.