drag and drop submit button is active before action is completed

True that this is not available out of the box. However using the Object actions you could achieve something leading to the same result. I suspect you are talking about a D&D slide used as Knowledge Check slides, not as a scored quiz slide. A while ago I wrote out a possible workflow to avoid that such a slide was submitted without having done any drag action. You can have a look at:

http://blog.lilybiri.com/prevent-skipping-on-drag-and-drop-quiz-slide

This may inspire you to extend it to reach your goal, not by deactivating the Submit button, but by giving a warning. Another possible tweak could be to make the Submit button invisible to the learner (no label, Alpha and stroke set to 0) and based on the tracking by the Object actions to show an image of that button on top of it when all the drag actions have been done. The 'invisible' Submit button remains active. That workflow cannot be used in a Fluid Boxes project however.

There is no option in Captivate to do this for Drag and Drop submit buttons.  Feel free to log an enhancement request and wait patiently for several years.