You can add assets to a campaign. While you cannot add at a contact level, you can add a static list. Be sure that the contacts that attended the off-line event are on a static list, go to the campaign, click the button to add assets, then associate that static list.
I’ve added contacts who attended the event to that static list and associated the list to a HubSpot campaign. This is working fine. However, I’d love to list this event on the activity timeline of a contact. This will also generate a notification to respective contact owners. Is this doable?
Whenever a contact is added to a static list or active list, that will be visible on their activity timeline as long as the “List Membership” box is checked. Using workflows, you can send a notification to contact owners as well.