Hi Nathalie,
My sincerest apologies for the delay! I’ve been conversing with fellow support team members on the matter and it appears I’ve been a little confused. By design, the plugin does not update fieldsets to avoid losing existing information in the attendee reports. I did some more testing and was unable to reproduce the behavior I described in my previous response that I updated a fieldset and saw the changes successfully reflect across all events with that fieldset. I truly apologize I misinformed you about how the plugin works and if I caused any delays on your project.
I don’t have a readily available snippet to alter how the plugin handles updating fieldsets across all events, however we do have a list of customizers available for hire should you need to go that route.
Again, I feel terrible I’ve sent you on a wild goose chase and wish you the best of luck making the changes you need. This definitely is a feature I see value in, so I recommend visiting our UserVoice Feature Ideas and submitting it as a feature request.
Thanks for working with me on the “issue” and your patience throughout the conversation. Take care and please feel free to create a new thread if you have any more questions or concerns.