If I understand you correctly you want to log in as a user and only see the suppliers of that user and not all the suppliers in the system? If so than you need to constrain the suppliers. You can do this with a XPath or with a datasource microflow where you retrieve over the reference of the user all the suppliers. And when creating a new supplier you have to make sure that the reference is set. Depending on how you build your forms the system will set this reference automaticly.