Beside value mapping used in frontend I would like to have something similar for use in simple macros within triggers.

Think about applications with a lot of error codes like Oracle error messages or messages produced by Tivoli Storage Manager.
These kind of messages can appear in many different flavors:

• Code + Message
• Code only
• The previous two produced and mixed with upstream applications
• ...

I would neither want to use triggers with common filters like .count(5m,"ORA-")#0 => A common Oracle error occured... nor to create thousands of triggers with exact filters.

I think about the possibility to import one generic mapping definition per application (Oracle, TSM,...) that might be used to map thousands of error codes to error messages.
These could then be referenced via simple macros by a new function especially for this purpose like {host:key.mapstr("String map name")}.
Another use case might be for example vfs.file.regexp[file,regexp,<encoding>, "String map name"] for passive agent checks with this item.

This way one could define very generic triggers with pretty messages even on varying error code positions in item values.