Is this a savegame node you want to use to store user data, or is this a web-based database you want to use to store data?
What I do to store user data, is to create a single string with special characters, store it in an array, and on load read the array containing all strings, then split the string according to the special characters I placed. The string information can be translated back into integer values. The easiest way however to save user data (the library) would be to create a savegame state, which would save user data locally.
To create a copy of an actor use the Spawn Actor from Class node, pick the default actor, then update the actor with the user modified values. This would be done depending on how your actor is setup, ie. based on structure values, or on various variables. Basically when the user changes something you need to create a variable for it and store the modified value there, then copy this into the “placeholder/storage” actor on game load or at runtime.