This would make things so cool, but too late for this next release, something to think about though that is if it is easy. If it's a lot of work then ignore.
I use Lightroom photo editing package, it has a lot of sliders for params or you can enter a number directly. Similar to JWF in some ways. It has a simple but great way of restoring a value for a param to it's default number.
So say the dist value has been altered to 3.4 or something but you want to quickly reset the dist value back to 0. You double click the name dist and it resets the value back to 0.
I'm assuming there are default numbers for each value of a variation stored somewhere? If so, could it be that double clicking on the value's name would reset it?
Could also click the variation number to reset all it's values to default?
When tweaking, often you need to go back to the default values, but unless you remember what they are you can't. You can always delete the variation and add it back again but the way I suggest would make that so much quicker.
Just a suggestion