To better assist you, I'd like to gain some more insight about your question. Which new feature are you referring to? Would you be able to provide a screenshot? Providing a few more details will allow me to assist you to the fullest.
In the meantime, I recommend you using a private browser when accessing your QuickBooks Online (QBO) account. This is to verify if this is caused by the system or your browser.
You can use the keyboard shortcuts below:
Internet Explorer: Ctrl+Shift+P
Once done, try to create an invoice again. Check to see if you're now able hide the new feature prompt. If they are, then your main browser may have too much historical data from previously visited websites which slows down internal processes and causes this kind of behavior.