Custom Attributes

Read the doc:

https://www.e-dynamics.be/wordpress/?cat=29

Thank you, I found that myself. But for custom attributes to work I have to edit them in MY BACKEND.

You did not specify anything like a use case in your question. Custom attributes are part of the event creation and format settings, so you need to do it from ther backend.
Any feature requests should bemade at https://www.e-dynamics.be/bbpress