As an example:
A struct holding 30 or so other variables, last one is another struct that holds just material information of this object.
Data Tables also use them, so you can load a struct from a DT - a template data for an object, construct the object based on the pulled data, modify the data and then save it using the very same struct. Not back into a Data Table, though - save in the game instance if it’s temporary / transitional data to be stored during a session, or save into a save game object if it needs to truly persist - be loaded next time the game is launched.