If you need to send an email or notification manually you should go to Booking View page. Click on More Actions. Select Send Email. You can use an email template or compose your email.
You can also to add more frequently used templates to Send Notifications and send them from there. To add a template to Send Notifications:
1. Go to Inbox-> Trigger Rules and select the trigger rule as Favorite.
2. Go to Booking view page.
3. Click on Send Notifications.
4. Select the notification.