In case anyone has this same issue, I've contacted Squarespace support (live chat) and they derived me to email. Haven't heard since.
I've found a workaround: using the "old editor" (not the beta one) lets you both rename options and reorder them. I hope this is possible in the new one, because it's a super basic thing to ask for. Will still wait for an official response.
Last update (for now) in case someone in the future stumbles upon these problems: official response told me that you can reorder variant options within the modal where you add/remove variants (you can drag and drop the pills around). On the other hand, option name editing is currently NOT possible with the beta editor.
Workarounds are:
* As I said before, using the classic editor (I think this is best).
* Creating another option with the new name, reorder it to leave it where you want (with the beta editor).
