YITH WooCommerce Request a Quote allows to activate a quote request system for users in your shop about one or more selected products. The plugin has been planned to give a better help to your customers when they make a request about the total cost of their order.

Quotes are sent by email and, if you want, you can attach a PDF copy of it for a more professional appearance. You can also choose between giving the chance to request for a quote to all users in your shop or only to registered users with a specific WordPress role.

Read this user guide to learn more about what the plugin allows you to do and to solve any possible doubt arisen during use.

All Setting detail please refer this doc –https://docs.yithemes.com/yith-woocommerce-request-a-quote/

If you are need add to quote work on variable products.
Please refer below:

  1. Install – Remove Add to Cart WooCommerce – https://wordpress.org/plugins/remove-add-to-cart-woocommerce/
  2. Change the Zero / Free Price to another text , please add this code into function.php :

    // add_filter(‘woocommerce_get_price_html’, ‘changeFreePriceNotice’, 10, 2);
    function wpgeeks_price_override( $price, $product ) {
    if ( empty( $product->get_price() ) ) {
    /*
    * Replace the word “Free” with whatever text you would like. Also
    * remember to update the textdomain for translation if required.
    */
    $price = __( ‘Available Upon Request Only’, ” );
    }

    return $price;
    }
    add_filter( ‘woocommerce_get_price_html’, ‘wpgeeks_price_override’, 100, 2 );

  3. Quick View – Remove Add to Cart if your stock is in “0” mode instead of OUT OF STOCK.

    Add CSS –

    .single_add_to_cart_button.disabled.wc-variation-is-unavailable {
    display: none;
    } 

    Next please add code to – function.php

    add_filter('remove_add_to_cart', 'my_woocommerce_is_purchasable', 10, 2);
function remove_add_to_cart($is_purchasable, $product) {
        if( $product->get_price() == 0 )
            $is_purchasable = false;
            return $purchasable;   
}


function remove_add_to_cart_on_0 ($purchasable, $product){
        if( $product->get_price() == 0 )
            $purchasable = false;
        return $purchasable;
    }
add_filter( 'woocommerce_is_purchasable', 'remove_add_to_cart_on_0', 10, 2 );

You also can read more about remove add to cart in different senerio – https://quadlayers.com/remove-add-to-cart-button-in-woocommerce/