Adding/modifying extra users for SFTP

I recently found out that you can transfer files to the CoBot using SFTP. This works very nicely.
Now i would like to change the password of the root user and to create an extra user that only has access to the directory where you would place your scripts in the CoBot. This way nobody accidentally messes with files they shouldn’t.
Does anyone have a tip on how to do this?
We have a UR5 and a UR10.

Kind Regards,