Hi Plantsmylove,
I don't know what climate you are in but you might look at Borage. It's a great companion for both tomatoes and squash. It gets so hot where I'm at, it's hard to keep borage growing in the summer, although if you grow it amoung the squash and tomatoes, it may get some shade.
Bee Balm is another good choice, and it will attract pollinators for your squash plants.
Borage and Bee Balm (Monarda didyma) are both edible herbs.
Happy Gardening!!
