I just read the thread again and I'm not sure you need a new user to perform the changes. You can use the bitnami user to edit any files in your system as it has administration privileges. Could you please let us know which files you are trying to edit and the current permissions of those files? You can obtain the permissions information by running this command
sudo ls -la /path/of/the/file/you/want/to/edit
I think Filezilla also shows the owner user and group of the different files of the folder it's displaying.