In OutSystems you can use Popup Editor widget to show out of the box popup on client event of any link or button.
When I was learning to do the same I faced one problem and noticed that this can happen to anyone using OutSystems for the first time.
When you drag and drop Popup Editor widget on an screen then you can set its property named LinkOrButtonWidgetId so any link or button on same screen. But I was not able to see my button in the list displayed for this property so I was not able to get this pop feature work. After searching a lot I got frustrated but nothing worked so I tarted hit and tries and then I notice that I forgot to set the name property of my button that is why it was not displayed in the list. After that I set the name of button and bingo… I was able to see it in the list and it worked.
The same solution above works even if your button is inside any list record or table record. So if you want to open a popup upon click on an button or link in OutSystems don’t forget to set its name property.