I was re-thinking this and maybe what you can do is to use a low priority in your 'default' flow and as a confition just add 'return true == true;'. The flow containing the real logic must be always evaluated first, so it must have a higher priority.
I've checked the Eclips plugin and what you have there is a 'Always true' checkbox that creates the condition 'eval(true)'. You still have to use a low priority if you want to use this as a 'default' flow.
Hope it helps.