What plan do you have for Workers? I believe these notification options are based on the subscriptions on your account. It would not surprise me, for example, if you could not create a billing notification for a product on a Free subscription. The option only appears for me where I have a paid Workers subsctiption that is usage based.
Interestingly, the dashboard actually suggests to create the notification ever since the worker was made, but it doesn’t appear in the drop down when I go to do that.
This is what “kian” on the Discord showed me the option should look like, if it existed, above the Durable Object stuff. But my list doesn’t have this entry for some reason.