Use [dokan_vendor_dashbord] shortcode to show the "Go to Vendor Dashboard" button on any page you want when a vendor is logged in.

functions.php

<?php
add_shortcode( 'dokan_vendor_dashbord', 'dokan_show_vendor_dashboard_url' );
function dokan_show_vendor_dashboard_url() {

    if ( ! dokan_is_user_seller( get_current_user_id() ) ) {
        return;
    }

    printf(
        '<p><a href="%s" class="dokan-btn dokan-btn-theme vendor-dashboard" >%s</a></p>',
        esc_url( dokan_get_navigation_url() ),
        esc_html( apply_filters( 'dokan_set_go_to_vendor_dashboard_btn_text', __( 'Go to Vendor Dashboard', 'dokan-lite' ) ) )
    );
}
?>