Hey JP, You can use the workflow action ‘Element Actions --> Display Data’ for this.
Here is a forum example with workflows (there isn’t any test data in preview mode at the moment, but the workflows would be similar for your app):
In this example, there is a repeating group of Users on the page. Within each cell of that User Repeating Group is an image element, with the data source “Current cell’s User’s Profile Picture”. When that image itself is clicked, a Popup opens which displays that User’s Photography (list of images) within a repeating group (type: image). To display the most recently-clicked on User’s photography (list of images), you would set:
The popup’s type of content to User (the type of content of the popup matches the type of content of the page’s repeating group).
The repeating group within the popup’s content type is Image, and the data source is “Parent group User’s Photography”.
Then create a workflow when the User’s Profile Picture is clicked:
“When Image A is clicked”:
1st action: Element Actions --> Display Data --> “Element: Popup, Data: Current cell’s User”
2nd action: Element Actions --> Show Popup
This workflow action changes the Popup’s data source (which User’s Photography is being displayed), thus changing the list of images displayed in the popup.
And that should work! If any of this was confusing at all, please feel free to share a link to your app and we can definitely assist with setting this up!