Automatically loading of user's "@" handle in the reply box when the Reply button is clicked.

Hi pp_01 

I don't believe this is possible with any out of the box admin settings. You could add this JavaScript as a custom component to the Forum Topic Page. When a reply button is clicked it will grab that messages' id and make an API call to get the author info. Then it adds the mention to the reply editor.

<@liaAddScript>
;(function($){

    var replyButtons = document.querySelectorAll('.reply-action-link');
    var ed;

    for (var i = 0; i < replyButtons.length; i++) {
        replyButtons[i].addEventListener("click", (event) => {
            var reply = event.target;
            var message = reply.closest(".lia-message-view-wrapper");
            var messageId = message.getAttribute("data-lia-message-uid");
            var url = "/api/2.0/search?q=SELECT%20author.id,%20author.login%20FROM%20messages%20WHERE%20id%20=%27" + messageId + "%27"

            tinymce.on('addeditor', function(e) {
                ed = e.editor;
                
                    async function fetchAuthor() {
                    const response = await fetch(url);
                    const resp = await response.json();
                    console.log(resp)
                    var atMention = '<p><li-user login="' + resp.data.items[0].author.login + '" uid="' + resp.data.items[0].author.id + '"></li-user>&nbsp;</p>'

                    ed.execCommand('mceInsertContent', false, atMention);
					var bm = ed.selection.getBookmark();
                    ed.selection.moveToBookmark(bm);
                }

                fetchAuthor()

            })
            
            

        })
    }

})(LITHIUM.jQuery);
</@liaAddScript>