[votan]

After taking a look I would suggest:

local orgShowContextMenu = SharedChatSystem.ShowPlayerContextMenu
    function SharedChatSystem.ShowPlayerContextMenu(...)
        local orgClearMenu = ClearMenu
        local orgShowMenu = ShowMenu
 
        if not ZO_Dialogs_IsShowingDialog() then
            local chat, playerName, rawName = ...
            function ClearMenu(...)
                ClearMenu = orgClearMenu
                ClearMenu(...)
                -- Here: Insert items before
            end
            function ShowMenu(...)
                ShowMenu = orgShowMenu
                -- Here: Append items
                return ShowMenu(...)
            end
        end
        return orgShowContextMenu(...)
    end

But without warranty