Drag and drop file upload on TreeTable

I wish to drag and drop multiple files from outside the browser (from OS file system) on to a row in a TreeTable so that files get uploaded and get added as children to the row dropped on in the TreeTable.

I referred to below code sample which allows drag and drop of files onto a imageBox:

How can I have drag and drop of files to a row in a TreeTable and handle the uploaded files?

Please help by providing some direction on how it can be done. Thanks in advance.