I want to tag users in the comment box (text box) by typing @, and similarly send an email notification to them if they have been tagged.
Also typing @ must show list of all available user and that list should change as per the typed characters, for Example "@ad" must show all the available users with "ad" in there name
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As far as I know this is not possible at this moment. Have a look at the latest release training. There could be something which you can do based on latest features coming in 24.3
Hii adityan0002 you can go through this discussion, i hope you'll get your solution require-tips-on-implementing-mention-tag-functionality-in-appian-in-text-and-paragraph-fields.
This functionality is now available out of the box using Record Events and the Events History List component docs.appian.com/.../Event_History_List_Component.html