In order to be able to create multiplation on several structured elements (...)*X +(...)*Y I would like to suggest to integrate the "command line" option with Emmet. Perhaps, there could be a option in settings (integrate CLI with Emmet) and if the user switches this ON, you could type the Emmet commands in your "cli". Basically it would make the command line field as an "extension" for the Emmet input. And when it comes to the documantation - just redirect to Oxygen site for more information.