I’ve had this article saved because I’ve been looking for new ideas, too:

https://homeguides.sfgate.com/plants-survive-winter-window-box-47953.html

I’ve never had any of these, so can’t vouch for them.

At my last house, I had a very deep and wide iron planter, and had rosemary in it that I kept trimmed to the size I wanted. I cooked with the trimmings. :) Iirc, I initially planted three 4-inch pots along the back (it grows fast).

It did great, and I’d plant annuals in front for each season. I’m not sure how rosemary does in winter in your zone .... in my experiences, it stays evergreen, doesn’t brown in 100+ temps/full sun, doesn’t suffer from being somewhat root bound (of course there are exceptions), and is drought-tolerant. I’ll probably end up using it again for my current window planter, since it’s so dependable.

Here’s another article about winter containers

https://www.finegardening.com/article/10-plants-for-year-round-containers