It would be immensely helpful if there can be a way to display the 'Manually Configure Fields' section of Union tool to the App user.
Something on the following lines - User uploads few files and then a window opens up onscreen which allows the user to 'manually configure fields' just like it is visible in the Union tool in a workflow. Its best use case is where we have a template with defined headers and the user just need to upload a new file/files and align the incoming fields correctly with the blank fields of a template.