System.setGlobal/getGlobal is only useful for storing string data. This can be useful for integer/boolean values but you have to remember to cast them from string back to correct type when you use System.getGlobal().

Object storage is a bit more difficult.

However, thanks to Rusty Fobe we have utilities posted in the files section. With said utilities one can convert a javascript object/array into a string format that can be restored using javascript eval. The serialization technique/notation used here is what has become known as JSON (Javascript Object Notation).