In the Botpress cloud API documentation I did not see an endpoint to add/update/delete knowledge base of a chatbot. Along other features in the API, I think, this should also be available with cloud API. I've gone through the docs about 3 times and did not see any such endpoint or information.

Knowledge base, flows, tables, etc are not exposed through our Public API just yet, this is why you couldn't find it. We want to get these features right for low code users (studio) at first, then once we feel confident about a feature set, we expose them as API. You will agree with me that it's much easier to change APIs without breaking users when nobody except the Studio uses them. Anycase, stay with us long enough, you'll get these APIs exposed

Yes, I do agree. Waiting...