Update "Add New" text

You can use a specific language pack and put it in /wp-content/languages/wp-idea-stream

Or filter ‘wp_idea_stream_reset_post_title’ and rebuild the entire title eg:

function gdOg_archive_title( $title, $context ) {
	if ( 'archive' !== $context ) {
		return $title;
	}

	if ( wp_idea_stream_user_can( 'publish_ideas' ) ) {
		// Your custom text
		$custom_text = "Whatever you prefer";

		$title =  '<a href="' . esc_url( wp_idea_stream_get_root_url() ) . '">' . wp_idea_stream_archive_title() . '</a>';
		$title .= ' <a href="' . esc_url( wp_idea_stream_get_form_url() ) .'" class="button wpis-title-button">' . $custom_text . '</a>';
	}

	return $title;
}
add_filter( 'wp_idea_stream_reset_post_title', 'gdOg_archive_title', 10, 2 );