Export custom fields from Multi customer booking

[Markus Schmied]

For a special scenario I need to export the custom fields for an appointment with up to 100 registrations. I figured it out for a single participant booking using the information provided in the discussion: Custom Fields in Microsoft Bookings - Microsoft Tech Community
Maybe @Martin Coupal, you can also help in this case ;)

Is there a way to get the information for a multi customer booking? 

[#2]

@Markus Schmied Hi, I have similar issue. I have time slot that is dedicated for more participants and some custom fields to be filled out as well but I am not able to extract the data.

I thought that this tutorial will help but it works only for "one participant" events.