How to show a popup in macOS? - Installation & Integration - Popupsmart Community
Safari allow pop-ups - possible to push?
With Safari, can I allow pop-ups for specific sites? - Ask Different
How to stop safari from opening tabs ? I watch a lot of pirated media and use AdGuard but when clicking the video it just opens another tab.
Videos
Wondering if there’s a way to enable pop-ups for specific sites that Mosyle can push out?
Have a specific educational site that requires pop-ups to function, with several grades/classes involved. While the teacher could do it one-by-one … not a good use of her time (She’s my rockstar and I’d walk hot coals to help her because she’ll drag the rest of them into the fray).
My first thought is configurator, but right now I have a USB-C Mac and an iPad with Lightning, so I can’t just plug it up and try - but if configurator can’t set this property there’s no good reason to run out and get the cable.
Better ideas always welcome — hoping I don’t have to give her what I expect will be bad news.
Yes, with Safari Version 12 or higher, you can allow popups for a specific website. Here are step-by-step instructions:
Right click on the URL (when you're NOT in a text entry mode)

Select "Settings for This Website..."
Select "Allow" under "Pop-up Windows"
There isn't any exception list for popups in Safari. It's an "all-or-nothing" approach for now.
I recommend telling Apple your thoughts on the Safari feedback page: http://www.apple.com/feedback/safari.html
EDIT 12/20: This answer is correct as of the time it was written. Since then, Apple has added the ability to control popups per site. This answer by @matt-chandler is the correct one for newer versions of Safari. I'm leaving this answer here in case it helps people on older versions of Safari.