Dry the greens to save for later use. I have what I call "wandering onions". They look much like yours, I have given several neighbors bunches to start their own onion beds, let the seed fall and make more plants, transplant until you have a nice bed. Mine is about 24" X 24" and gives me plenty to use for seasoning and "storing". If you do not want to dry them, freeze them in small ziploc bags to just dump into your recipes. Frozen easily lasts a year.You can cut the stalks and cook with them.
I had cut onions back several times and used the stalks for soups.