Click on the select products button in the quotation/sale order form view.

When you click the select products button, the select products wizard will open.

When you click on add a line product wizard will open to select multiple products.
Click on the select button.

Now, selected multiple products are added in the select products wizard,
click on the apply button.

By clicking on the apply button products are added to the order lines in the sale order/quotation.

In the products list view, select multiple products and select create sale order from the action button.

It will open the create sale order wizard to add customer name.

The sale order is created and selected products are added to order lines with added customers.

In the product variants list view, select multiple products and select create sale order from the action button.

It will open the create sale order wizard to add customer name.

The sale order is created and selected product variants are added to order lines with added customers.