If we create a DocumentFile using the tree URI returned from ACTION_OPEN_DOCUMENT_TREE.
DocumentFile dir = DocumentFile.fromTreeUri(context, treeUri);
And then create a sub directory
DocumentFile subDir = pickedDir.createDirectory("example");
Uri uri = subDir.getUri();
How can we later recreate the sub directory using the above URI?
Figured it out, you have to use DocumentsContract.createDocument() with the URI of the previously created directory.