Hi Eneia ,
Glad to hear that it worked! 😄
"I'm looking at how to open a window inside a popup (always with Buttonizer !!)"
Sorry, I don't quite understand this question.
Would you like to open a popup? And inside this popup is a page of your site?
If so, you could maybe use Popup Maker and use an Iframe to display your page.
"When I finish the work on the site / platform can I insert the fact that some parts have been made with Buttonizer?"
As long as Buttonizer is installed and your site is running on a WordPress environment, it should be fine 😄