While there is no official in-game "mod menu" developed by THQ Nordic, players can access mod-like features through two primary methods: the Custom Quest Menu for game-altering mods and third-party tools that provide real-time cheat menus. Core Ways to Access Mod Menus
Some mod menus don't add new items but re-enable the hidden developer console. This requires console commands: titan quest mod menu
Just let me know which direction you want. While there is no official in-game "mod menu"