I'm 99.9% sure there is not documentation for what query string parameters are available because every module/page/control has different requirements, very similar to how you might create your own page or user control. For instance, while working in the content tab, it might be NodeID but in another module, it might be UserID or ObjectID. In one instance you might use a query string, in another, you might have no need for a query string.
Also, note that as Kentico evolves, the use of i-frames in the administrative interface may be removed. You can already see some of this with v8 in comparison to v7, so I wouldn't count on it always being there.