init.el recommendation of the day: (setq magit-list-refs-sortby "-creatordate")
Use universal argument before opening the transient, it gives you some options there. In general, many magit transients understand universal argument (C-u). Refs transient allows you some sorting and other things when invoked with an arg.
I have this in my config for most used values:
(dolist (v '((magit-pull "--rebase")
(magit-show-refs "--sort=-committerdate")
(magit-fetch "--prune")))
(add-to-list 'transient-values v))