You need to do some work, if you want to.
For which aircraft?
Example: A-10C
Browse: "...\Mods\aircraft\A-10C\Cockpit\Scripts" folder.
Find: Macro_sequencies.lua
Take a backup of it.
Edit it via Notepadd++ or another good text editor.
Erase message part of the line like below;
,message = _("BATTERY - ON"),message_timeout = std_message_timeout
You must do that for each command line.
Or, there may be an option in OPTIONS page. Turn off Subtitles or something?
Cheers.