Good evening and welcome back!
Thank you for reaching out to us.
I would love to help you with this topic.
You are absolutely right. The page that appears after the successful submission of the event is actually not a different page.
What you could do however is to redirect to a new page after a successful event submission.
One idea would be to adapt the following snippet for Community Events: https://gist.github.com/elimn/ffa84662d26faadb906dc5aea2a0896b#file-tribe_event_tickets_rsvp_success_script-php
You should find the necessary hooks in /wp-content/plugins/the-events-calendar-community-events/src/Tribe/Submission_Handler.php
Short term, if coding is not really your cup of tea, the only other workaround I could think of would be to do a view customization of the “Add Event” view and put your custom content there, just before the form (instead of in the Pre HTML section).
This way the additional content will only be tied to the “Submit event” form which should allow you to reach your goal.
You might want to read our Themer’s guide to get a sense of how that works.
Let me know if that helps.
Have a great day!
Geoff B.