Can I add a customized button in the popup window body

I have created a popup window, instead of the default two buttons at the bottom, I would like to add a button in the body of the popup window. Actually does it really possible to do so? If no, another other method / suggestion?

I have tried to insert some html code in the template but it didn’t work.
I would like to add a button like the grey button as shown in the diagram. Thank you for your time for reading my question.


Add the Button HTML code in the template part