nappa cabbage

my nappa cabbage bolted, can it be saved or is it just compost fodder?

Once a plant like cabbage for instance bolts, it won't unbolt, but not all is lost. If you desire your own cabbage seed, let it go. If you have livestock or chickens, they'll likely eat it. And of course, like you mentioned, composting is always a good way to make something useful out of something undesirable.