I've just seen from the Pico 8 wiki that there's a new while shorthand:
while (cond) actions

And yeah - it works.
But it's not documented anywhere in the manual - not in the shorthand section and not even in the changelog!

Side note: I'm the one who suggested it, and I'd swear I suggested two candidates for single-line formats similar to if().

I tried for(), but it doesn't work. I can't think of what else I might have suggested, and I can't find my post or tweet that suggested it. I think maybe it was for(), but maybe the various differed syntaxes (syntaces?) were too complex.