Append (or add) tags or text to selected tasks

of_tags.scpt

display dialog "Add tags" default answer "" with icon file "Applications:OmniFocus.app:Contents:Resources:AppIcon.icns"
set noteTags to text returned of result

tell application "OmniFocus"
	tell front document
		tell content of document window 1 -- (first document window whose index is 1)
			set theSelectedItems to value of every selected tree
		end tell
		repeat with anItem in my theSelectedItems
			if note of anItem is not "" then
				set existing_note to note of anItem
				set note of anItem to existing_note & linefeed & noteTags
			end if
			if note of anItem is "" then
				set note of anItem to noteTags
			end if
		end repeat
	end tell
end tell