[Lizard]

Here's an example of how to create a new action in OmniFocus. Hopefully you can keep the Mail parts of your script and then just swap in something like this script:

tell application "OmniFocus"
	set theDoc to default document
	set theTask to "Buy Cat Food"
	set theNote to "Salmon, not chicken"
	tell front document
		set theContext to context named "Grocery Store"
		set theProject to project named "Cat Maintenance"
		tell theProject to make new task with properties {name:theTask, note:theNote, context:theContext}
	end tell
end tell