Use this code example, which will allow you to set a new default page URL for a target form ID wherever the page_id attribute is not specified.

add_filter( 'frm_abandonment_edit_entry_url', 'set_default_page_url', 11, 2);
function set_default_page_url( $url, $atts ) {
    if ( ! empty( $atts['page_id'] ) ) {
        // Use the Page ID if it is set in the shortcode.
        return $url;
    }

    $target_form_id  = 6; // Change 6 to the form ID
    $default_page_id = 12; // Change 12 to the default page ID
    $entry_id        = $atts['id'];
    $entry           = FrmEntry::getOne( $entry_id );

    if ( $target_form_id === (int) $entry->form_id ) {
        $url = get_permalink( $default_page_id );
    }

	return $url;
}