If you have a listing saved as Incomplete (INC), Matrix will allow you to add a Tour or Open House to it. One thing to keep in mind: since INC listings are not visible or searchable for any other Matrix users, no one will see that Tour/Open House while the listing is still in the INC status. It will not be visible to any other users until the listing is saved as either Coming Soon or Active.
In the event that the listing is saved as Coming Soon, be sure that the date of the Tour/Open House is scheduled for after the listing is set to come on as Active. It is against SmartMLS Rules to show or have a Tour/Open House on a Coming Soon listing.