How do you store these? If I cut them and leave uncovered they dry out and if I close them in a lidded container they lose the crispy edges?

You really should store these sheet pan muffins covered / in a lidded container, to keep them from drying out and fresher tasting. If the edges are not as crispy as they were when first baked, and you really prefer them crispy, you could put the muffins in the oven - 325 degrees Fahrenheit - for about ten minutes. I'd do at least a few at a time, putting the uncut edges close together to keep the oven from drying out the crumb. ;o)