Hey Jordi,
Thanks for your interest in our plugins!
There is unfortunately no official back-end demo that you or other customers can log into, but there are two important caveats here worth sharing!
First is that we have a no-questions-asked refund policy if you request your refund within 30 days of purchase. This lets folks “try out” the plugin, so if you’re interested in this it’s a great option. You can buy a license, and fully install and begin using the plugin, and if you like it, just keep your license. If you don’t, all you have to do is request a refund and we’ll issue it immediately!
The second thing to point out is that The Events Calendar itself is free. You can download it here → https://wordpress.org/plugins/the-events-calendar/
Just playing around with the free version, if you haven’t already, might alone give you a really good sense of the plugin. Event creation and most front-end rendering of events is the same whether you have PRO installed or not, so the free core plugin alone might be a good option for you to demo with.
Do these suggestions help? Let me know! 🙂
– George