We have managed to cultivate the remains of a supermarket pot in the garden, so always have fresh parsley to hand. However, I do still have a couple of packets of frozen chopped herbs in the freezer.
Thawed out parsley, if frozen whole, as you describe, probably wouldn't look very good as a garnish, so it would have to be used chopped anyway.
You can freeze it chopped, loose, or in an ice cube tray with some water, or so I've heard. For salad dressing, it may even be possible to freeze it in oil. I make oodles of pesto every year and freeze that, and the main ingredient there is oil. I think I'll try that before the parsley in our garden gives up the ghost.
Ditto chives and, next year, dill. I had dill out there and used it a couple of times, but it went to seed, so next year I'll try catching it fresh and freezing it before it goes to seed. I wonder if any of the seeds will germinate and produce new plants?