In order to display a modal popup from another module, you will have to use a unique class name or ID that is shared between the Modal popup and the respective module.
1. In the Modal popup settings, under the Display settings tab, select to display the popup on a Custom Class / ID. You can find tutorial on how to create a custom class/ID for an element HERE.
2. Enter the unique class name in the text box below.
Note: Add a “.” before a class name and a “#” before an ID.
3. Make sure the same class name is entered in the Advanced Settings tab of the module you wish to use.
This method will display the modal popup on the click of the button or link in the other module.