This add-on will allow users with the appropriate permissions to add notes in their own threads only and/or in all threads. The notes can be a reminder, a to do list or anything else. It can also be used for the staff to keep track of a particular thing/situation pertaining to a certain topic(s).
After you install the mod go to the group(s) that you want to use the Thread Note System and when editing that group permissions, under the General tab, all the way to the bottom you will see 2 new permissions setting added:
1) Can add notes in own threads only:
2) Can add notes in all threads:
Set them accordingly and save the changes.
Then users with the right permissions will see the Note link in thread view.
The Administrators and Super Moderators can receive an alert whenever someone adds and/or removes a note from a thread(s). This option can be enabled and disabled at Settings->Options->Threads, Discussions and Conversations->Thread Notes Staff Alert!
For more info please check the attached screenshots.