Hi,
As I understand it, the invitees you refer to are the contacts who sent the specific event invitation emails.
And as we know, if records is supposed to be shown in the form of another entity, there should be a 1:N (one-to-many) or N:N (many-to-many) relationship (Event: Invitee) so that they can be listed as a subgrid.
The invitees here are in fact the contacts.
There is a 1:N relationship between the Event entity and the Contact entity itself, but that is a lookup field that is automatically filled in when a contact is created by registering for an event rather than what we need.
So we have to create a relationship between them.
A contact can receive multiple invitations from an Event, and an Event can invite multiple contacts, so the relationship between them is N:N.
However, this will result in the lookup view not being available when the subgrid is created.
So to implement your requirements, you can only create a 1:N relationship between the Event and Contact entities.
This means that if a contact is invited to more than one event, only the latest invitation will be kept.
Then create an on-demand workflow targeting at Contact entity.
Here, it can only be set as a fixed event cause there is no way to get a dynamic value, which means that you need to set it for every event.
After saving and activating the workflow, it can be inserted into the customer journey which sends the invitation emails.
Create the subgrid in the event form. Save and publish the form.
Finally, the subgrid of the invitees can be shown in a certain event form.
