[rules-users] Reusing Rules in a Rule Flow?

Is it possible to use a rule in a rule flow without a "ruleflow-group"? Here's our use case:  We have a base set of rules that are not part of a ruleflow-group.  But we want to allow the administrators of the system to build custom rule flows that reuse these existing base rules.  In most instances the "base" rules will be fired but in some instances the ruleflow will be executed too. What's the best way to reuse a rule in this case? Thanks! Jason