Teams Premium Webinars: Multiple 'Webinar Reminders'

Is it possible to create multiple 'webinar reminder' emails such that we can issue reminders to delegates 1 week, 1 day and 1 hour before a Teams Premium Webinar is due to start?

The stack of email templates only shows one option for 'Webinar reminder' so we are looking to add more. In the event that this isn't possible natively within Teams Premium, are there alternative ways of achieving this?  I wasn't able to find an option that might work in Power Automate for example...