Add internal notes to blog posts

I have a couple of blog posts that have done quite well because of factors outside of the obvious and I'd like to note on the blog post where this additional traffic has come from (so when I'm looking at trends 6+ months from now I can drill down and see the info without needing to just remember it)

Analytics has a version of this with annotations but I can't find anything similar within HS. 

The ability to add internal notes against content as well as companies/customers would be really helpful

HubSpot updates