Hi,
In context of class or component diagrams it would be nice to provide ability to create note also on a group of components like package, rectangle, frame, cloud or database.
For example:
@startuml
package "Package P" as P {
component "component A" as CA
interface "interface 1" as I1
I1 -- CA
}
note left of P : note on package P
@enduml
Thanks