Michael, can you elaborate on the need for the custom object? Is there a reason you wouldn't store this information using program/campaign member status? What do you ultimately want to do with the information surrounding their event registrations?
Glad to elaborate. The custom object is not a marketo one, but rather a SFDC Account related custom object.
To your question 'What do you ultimately want to do with the information surrounding their event registrations?'
I want to report which accounts are attending the show, not a campaign member report. We've tried and it gets messy because the members have a one-to-one relationship with the account so if you summarize by Account Name, you wind up getting the number of records that are attending per account. And in the dashboard it throws off the total numbers because it counts records per account not unique account name. **sigh, i wish SFDC had count unique functions**
So anytime the first person for a given account registers I want to pass/create a custom object that is essentially flagging the Account as "Going to the 2019 Event" but I dont want to pass any subsequent records.
I agree with Tara. You cannot create custom objects natively using Marketo. Seems like a SFDC campaign should work just fine for these purposes.