Hello @alicanyildizcom,

I am sorry for being late. If you want to use any third-party plugin to create the vendor role or a custom role with vendor capabilities then you have to make sure that you have added below capabilities for the role to provide access on Vendor operations –

 add_role( 'seller', __( 'Vendor', 'dokan-lite' ), array(
            'read'                      => true,
            'publish_posts'             => true,
            'edit_posts'                => true,
            'delete_published_posts'    => true,
            'edit_published_posts'      => true,
            'delete_posts'              => true,
            'manage_categories'         => true,
            'moderate_comments'         => true,
            'unfiltered_html'           => true,
            'upload_files'              => true,
            'edit_shop_orders'          => true,
            'edit_product'              => true,
            'read_product'              => true,
            'delete_product'            => true,
            'edit_products'             => true,
            'publish_products'          => true,
            'read_private_products'     => true,
            'delete_products'           => true,
            'delete_products'           => true,
            'delete_private_products'   => true,
            'delete_published_products' => true,
            'delete_published_products' => true,
            'edit_private_products'     => true,
            'edit_published_products'   => true,
            'manage_product_terms'      => true,
            'delete_product_terms'      => true,
            'assign_product_terms'      => true,
            'dokandar'                  => true,
        ) );

You can check details about the role function in dokan-lite/classes/installer.php and the function is – function user_roles()

I hope this will help you.

Cheers!