You can modify this template to set the default shipping address.

**vendor/magento/module-checkout/view/frontend/web/template/shipping-address/address-renderer/default.html**

Find out the template and modify it like this 

    <div class="shipping-address-item" data-bind="css: isSelected() ? 'selected-item' : 'not-selected-item'">
       
        <div>
            <span>Street: </span>
            <span>Your Specific Street</span>
        </div>
        <div>
            <span>City: </span>
            <span>Your Specific City</span>
        </div>
    </div>