Just got this working.
It creates a task where the title is the email subject and the body is a link to the email.
Not sure how I can add the macro here, but here’s a screenshot and the fragment of AppleScript that collects the message link:
tell application "Mail"
set _sel to get selection
set _links to {}
repeat with _msg in _sel
set _messageURL to "message://%3c" & _msg's message id & "%3e"
set end of _links to _messageURL
end repeat
set AppleScript's text item delimiters to return
set the clipboard to (_links as string)
end tell
