Are you using the new creation wizard? There you do not get a drop down. The rules are shown at the top of the wizard.
The screenshot shows one nameing rule with two patterns. If you want to add more nameing rules you have to check the online help for the different conditions that can be applied.
If you want to have multiple naming rules that generates an id from a serie it will show you a dropdown next the the New button so you can select which one you want to use.