This feature can be accessed from the ⚙️ More Options Button.
In Block URLs Text Field, you need to enter one URL per line. This field also accepts wildcard.
Here are some examples:
Make sure you only enter One URL Per Line. Press the Enter/Return Key to go to the next line. You can enter a maximum of 10 URLs in this field.
Here's an example of how the text field should look like if multiple URLs are blocked: