From within the detail page of an account record, we can select the New Pre-populated Opportunity selection, as shown in the following screenshot:

When we click on New Pre-populated Opportunity, a dialog window is presented with the Close Date already set as the current data plus 21 days according to the value of the Lightning Action pre-defined field values Close Date selection, along with the sales Stage pre-set to Prospecting according to the Lightning Action Predefined Field Values.

The dialog window can be cancelled to return to the Opportunity page by clicking on Cancel, as shown in the following screenshot: