Briefer melee messages
 

Is there a command to have briefer combat messages?

Yeah, the Hit Modes filter at the bottom of the window options when you right click a chat window. You can set normal, abbreviated, or number only.

If we were using an era-appropriate client when /hitsmode first came out, you used to be able to set up a window just for combat dialogue.

Here's an example page of how you used to set it up - http://www.jaburt.com/eq/hitsmode.htm