Drag and drop to upload tax docs to data import

[taxmo]

When you are working on a new tax return with no documents yet, there is a box in the "data import" window where you can drag and drop files to upload tax documents.  But strangely, after you upload any documents, the box to upload tax documents using drag and drop disappears, and after that you have to use the "upload more" button.  

I would like to be able to continue using drag and drop to submit new tax documents, not just when no documents have been uploaded yet.