There's a core module called "ConditionSwitcher", although I think it may be marked as a prototype. It takes a param that basically gets evaluated as a Javascript statement. So you can put things in it like '(context.get("someToken")=="all")'. Based on how that evaluates at runtime, it'll show different subbranches of XML config.
If you're using Sideview Utils 2.0, there's a much more powerful mechanism though, involving the Switcher module (new in 2.0), and depending on your use case, also the ResultsValueSetter module. Email me if you want to know more. (Sideview Utils 2.0 isn't a free product anymore so I won't spell it out here or you'll think I'm pitching you.) Cheers.
