:-) Oh no! it’s not the real Mudfish does. I need to update the site content seriously haha.
urban dictionary always dirty :D
Under requirements Data plan of your account should be ‘Pay Per Traffic’. If your data plan is ‘Subscription’, it’s not available.
It’s information out of date. Now Subscription data plan also can create the custom item. 
If there’s any problem to create, please let me fix it for you.