The macro uses AppleScript and within it interacts with System Events. For more information, check this out:
Mac Automation Scripting Guide: Automating the User Interface
I've updated the macro to Version 1.1. It now has a variable for the File Extension. Download this macro and change the value of local_FileExtension to docx.
DOWNLOAD Macro File:
Create New ReadMe and Edit.kmmacros (16 KB)
Note: This macro was uploaded in a DISABLED state. It must be ENABLED before it can be run. If it does not trigger, the macro group might also need to be ENABLED.