Hello S.,
Here is a workaround, using sub-diagram, as:
@startuml
label l [
{{
salt
{
<&person> Login | "MyName "
<&key> Password | "**** "
[<&circle-x> Cancel ] | [ <&account-login> OK ]
}
}}
]
note right of l
//note right//
On this form.
please to put * on
Password field
end note
note bottom of l: //note bottom//
@enduml
If that can help,
Regards.