The UID manager is a useful tool to get a comprehensive overview of all the unique identifiers (UIDs) used by your project. It will list all page, object and sound UIDs as well as UIDs used by the Animate object and Choose file to open action events. Furthermore, it will also list all variables used by the Set variable and Get attribute action events. This should make it much easier for you to make sure you don't use the same variable or UID name twice.