I'm not a developer so i can't suggest where to search exactly. Maybe you can take a look at Spark's Fastpath plugin. In Fastpath it was possible to have the Canned responses which in turn appeared on Spark interface, so an agent was able to select a predefined response by selecting it from a list. Seems similar to what you want. Spark was pulling those responses from the server, but you can probably modify it to use a local list.
By highlight you mean automatically highlighting keywords in a chat? Again, you can try looking into Spark' group chat code (MUC) as it can highlight your nickname (adding yellow background) when it is mentioned in a chat.
