Soumya,
Since this widget shows what items are currently in the reference set that the widget is pointed to, you can do this as follows:
- Create a microflow to open this page
- In the microflow, retrieve all of the values that *could* be in the reference set (i.e. all of the objects in the entity you are selecting)
- Now populate the reference set with the list you just retrieved via a Change action in the microflow
- The last step in the microflow should open the page
You will see all of the values selected on the page.
Hope that helps,
Mike