Recursive Open
NameChanger's open dialog offers two ways to add selected folder contents.
To reveal these options you may need to click the Options button on the bottom
left of the open dialog.
Open folder contents
Checking the "Open folder contents" option will take just the top level items in whatever directories you select.
Recursive
If you check "Open folder contents" AND "Recursive" then it will add all the
files found in the selected folders and nested subfolders. No folders will be
added, only files within those folders.