I want to take the form designed using the drag and drop designer in QGIS, into Qt Designer to modify it further and then bring it back into QGIS. Is this possible?

As per
https://gis.stackexchange.com/questions/338672/saving-qgis-form-design-basic-functionality-in-ui-to-modify-it-with-qtdesigner

I understand that QGIS can only export QML and not .ui files. 

Is there some other way of connecting the 2 or do I need to start from scratch in QT?