@Manny115
Please contact Airbnb and provide Feedback about inability to add notes to the regular calendar. You can add notes to reservations, but not blocked nights or open nights. I'm told they realize this is a bug and are working on it.
In the meantime, you can add notes by turning ON professional Hosting tools and adding a note to the date on the multicalendar. Once a note is added (includes previous notes for dates that are past) you can hover over a date with a dot and see the note. The multicalendar is only available on desktop; not the App:



