Get text filter that replaces text strings with a string customized by the administrator.

pmpro-gettext-filter.php

/**
 * Testing if this is synced or embedded
 *
 */
add_filter( 'gettext', 'my_pmpro_gettext_changes', 20, 3 );
function my_pmpro_gettext_changes( $translated_text, $text, $domain ) {
	$original = 'Drag and drop membership levels to reorder them on the Levels page.';
	$replacement = 'Whatever I want to replace that text with';
	$text_domain = 'paid-memberships-pro';
	if ( $text_domain === $domain ) {
		$translated_text = str_replace( $original, $replacement, $translated_text );
	}
	return $translated_text;
}