Thank you Shay Shmeltzer-Oracle
I have used custom renderers and also an oj-input-date to get the desired format, so that was solved.
Where does the attached UI appear? is that part of a custom data provider fetch action or something else?
This UI is the parameter mapper in the Assign Variable action in an action flow.
Have a look at the video here:
Around 15:30 to see how we use this when calling a REST service and processing the returned value.