In the "Create Object-Specific Quick Actions" Trailhead exercise I am stuck on the step bolded (Step 3). 

1. Enter Tab in the Quick Find box, then select Tabs.
2. In the Custom Object Tabs list, click New.
3. In the Object dropdown list, select Property.
4. For the Tab Style, select Real Estate Sign.
5. Click Next. Accept the defaults, then click Next again.
6. Click Save.

I have already created a Property custom object from a previous Trailhead exercise, and have double checked the Property custom object and can't see any reason why it wouldn't show up in this list.