Hi @Diana3114 , the workaround currently to edit and make notes is only accessible via the multi-calendar. If you don't have access to that, simply search the help pages for professional tool opt-in.
I have only half solved this problem, because after activating the "professional tools" I can now again add a note to a blocked date on the calendar.....I just can't remove/edit an old note! So now I have two notes on one date!