Following recent update to Phone- Version 6.0, you can't move Bookmarks to an already created folder in Secret Mode in Samsung Internet.
If you want to move Bookmark to a folder, the only option is to 'create subfolder'- usually it shows a dropdown with folders already created.
I've tried it with passcode on to access Secret Mode but this doesn't make a difference.
You can move bookmarks with regular Internet, just not in Secret Mode.
