Not sure this is a bug; will post it anyway.

I added a Codemirror field on my form but it doesn't show the "description" of each option. You can reproduce it in Nexus -> Products -> Custom Fields -> Email content for after purchase.

			$form->add( new \IPS\Helpers\Form\Codemirror( "p_email_{$k}_html", $this->$valueKey, FALSE, array(
				'preview' => \IPS\Http\Url::internal('app=nexus&module=store&controller=packages&do=emailPreview')->csrf(),
				'tags'	=> array(
					'{$purchase->name}'			=> \IPS\Member::loggedIn()->language()->addToStack('ps_name'),
					'{$purchase->expires}'			=> \IPS\Member::loggedIn()->language()->addToStack('p_email_tag_expire'),
					'{$purchase->renewals}'			=> \IPS\Member::loggedIn()->language()->addToStack('ps_renewals'),
					'{$purchase->custom_fields[1]}'		=> \IPS\Member::loggedIn()->language()->addToStack('p_email_tag_field'),
					'{$purchase->url()}'			=> \IPS\Member::loggedIn()->language()->addToStack('p_email_tag_url'),
					'{$purchase->licenseKey()->key}'	=> \IPS\Member::loggedIn()->language()->addToStack('license_key'),
				)
			), NULL, NULL, NULL, "p_email_{$k}_html" ) );

Every option has its "description" but it doesn't show in the form:

The value of each language bit should be displayed in the yellow area above.

Thanks for letting us know, we'll look to get this fixed in a future release.