Change Data Source on Server

I understand adding a parameter in PowerBI Desktop to change the connection string.  I need the ability for an admninistrator on the PowerBI Report Server to access and change the parameter.  I do NOT want to stick a user accessible/changeable parameter drop down on the screen that the users have to change.  I want this in the hands of the administrator.  The administrator already has access to the data sources and can set a user name/password for each data source.  I see no ability for an administrator to access parameters.