It would be fantastic to be able to add notes to the calendar, such as "early checkin" or "water heater repairman coming today", etc without blocking the date. Want to make it REALLY FANTASTIC and possibly less work to code? Overlay a Google Calendar on top of the booking calendar!!! Then we can put whatever we want on the Google calendar and see it overlayed with bookings. I am getting excited just thinking about it. I know we can already do the reverse, but it's not as good because in google calendar we can easily click on bookings and navigate right to what we need
This kind of functionality would be part of our Housekeeping and Maintenance module that we're hoping to have out sometime in the next year. It's been requested many times and would be widely useful, for sure.
Perhaps you could create a booking custom field for "Misc" or "Notes"? Then, when you run the Daily Checklist report you'll be able to see those notes.
I have a similar custom field we call "ETA" (estimated time of arrival). If the guest lets us know when they expect to check in we add that information to the ETA custom field on that guest's booking. Then each day when we run the Daily Checklist report we can see that information if the guest is checking in that day.