You can add things like this if you use the director plugin.
Actual real-world example we use:
We have a script that generates a CSV files of Access Points (APs) that Icinga imports and ties to a given customer container that is the Icinga “host”. APs are the “service” underneath the host.
Given the tools of choice (API or SNMP depending on AP vendor/cloud enabled), we scrape for the mac address, serieal, and some other information and import it all as properties (such as notes, etc…) under our sync rules.
If there’s a tool (or scripting knowledge on hand) available that will get this information for you and store it in any number of data types (ie Database, CSV file, etc…) then you can use the director to achieve this.
Director can also be used for “one off” note additions via the web UI. Going to Director > Hosts > Hosts > Select Host of Choice > Additional Properties > Fill in Notes field.
Of course, this wouldn’t scale well past a few dozen hosts unless you’re an MSP or something that can have some level 1s go find the info and paste it into the field.