There is a Listing Notes feature within Add/Edit that allows a list agent to enter a time-sensitive note to other Matrix users:
When entering a Listing Note, you have to enter the Start and End Dates and the Note itself:
The Listing Note will only become visible on the Start Date and disappears on the End Date.
Listings that have a Listing Note on them will have the following icon for the duration of the Note:
The icon will display in the section of displays that show other icons. For instance, on the Agent Full display, it appears above the photos:
You can add the Note Start Date field to the search screen (using Additional Fields) if you want to be able to search for listings that have Listing Notes: