You'll find this information in our rules, which you should have read already:
Standard world: On the Standard world all approved quickbar scripts are allowed that can be found here. All other quickbar scripts are forbidden. Userscripts are forbidden in general. Sandbox: Sandbox is especially designed for testers and script developers. Therefore userscripts are allowed on this world as well. You can use the quickbar scripts that have been approved on your market or that would be legal on your market if you should develop a new script.