To set up or add to the Property Status dropdown/List, You must first start in follow-up Property. For this example, I opened any property to get the Property Status field, to add to the list. 

Double the property Status Field to open Property Status list. Click the bottom line and type in the Status you want to add the list.

For this example, I added Construction to the list. Click Exit when complete. 

Back in the backoffice click the dropdown to confirm it's been added to the list. 

Now you can go to the Pre-Plan and the list should be updated for you to choose from.