Canned messages purpose is to provide prepared answers for standard questions. Canned messages can be found at
System configuration -> Canned messages
Also in admin windows you will see combobox with defined values. Also you can disabled canned messages adminsitrator by removing permissions access.
Also it's possible for operators to have personal canned messages, to them have to be assigned this permission. (Since 1.91v)
lhuser -> personalcannedmsg
Canned messages also supports these template variables. (Since 1.91v)
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