Vegetable steamer recipes? Well sauces?

Any sauce that you put into the steamer will be diluted by the moisture. It's better to prepare the sauce separately in a pan. If the teriyaki marinade is too strong by itself, then you can dilute it with water until it tastes the way you like, then make a slurry of cold water and cornstarch, adding it slowly to the sauce to thicken it over low heat while stirring it rapidly. Mixing cornstarch to cold water first prevents clumping that happens if you add the cornstarch to hot liquid.