Apple Contacts app no longer lets me create new lists or Smart Lists.

I have the same problem. Can only delete or rename or add contacts to the untitled groups on a different device after they sync. Work around for me is to create the groups locally, populate the group then move the group to the iCloud section. This can't be normal behavior.

Hey there Ljf101,

If you haven’t already, check for any updates to macOS. That can often resolve issues. Here’s how to update:

“Before following these steps, it's a good idea to back up your Mac.

1. From the Apple menu  in the corner of your screen, choose System Settings or System Preferences.

• If you chose System Settings, click General on the left side of the window. Then click Software Update on the right.
• If you chose System Preferences, click Software Update in the window.

1. Software Update then checks for new software. 

• If Software Update finds new software, click the button to install it. The button might be named Update Now, Upgrade Now, Install Now, or Restart Now, for example. You might then be asked to enter your administrator password.
• If Software Update says that your Mac is up to date, then no new software is currently available for your Mac model. Software Update shows only software that is compatible with your Mac.”

Update macOS on Mac

Restarting could have an impact on this as well. You can read how to restart in the following link:

Shut down or restart your Mac

Then just make sure you’re following all the steps in this link to create the Smart Lists in Contacts:

Create and change Smart Lists in Contacts on Mac 

Take care.