you can do about anthing you want. However okra is a huge plant (most varieties) Which can choke down the competition. I would not expect much from cantaloupes trying to compete with okra.

I grow trellised/tall plants in the same beds with shorter ones. I just make sure the trellised ones are not planted on the south side of the bed.

Forget the 3 sisters idea. It doesn't work for many reasons that are discussed in the many previous threads here about it.

But yes, IF you can plant so that the okra section of the bed doesn't shade the melon section - depends on how your bed lays in relationship to the sun position it could work.

You'd still have the different water and nutrient needs of the plants to contend with so separate them as much as possible.

Dave