By default, the pop-up block comes with one button.

The button should be added manually, Place the insertion point on the end of the first button.

Press enter key to start a new line. If we set a space or a tab it will extend upon the same button.

Write in the text for the new button. Select the written text and under the edit menu in the inline section select the add a link option.

Set the URL that the button will be redirecting to.

By default, the style would be a link, change it to a button.

The Enter should be removed to make the buttons on the same line.