You can manually edit a macro .txt file to insert the command “EditMetaData:”. This will bring up the MetaData window, but this macro command does not currently allow any options.
Note that “Specify metadata using Macro command” is one of the mentioned feature requests here: Missing features - Audacity Support
Even better, you could add your own feature request issue here: Issues · audacity/audacity · GitHub
See this post for additional insight: Macro/Scripting To Automate Metadata Editing