In Connector Xpress there is a 'Connector Map To' section with a dropdown list of Schemas. The schemas listed for MS SQL are dbo, sys and INFORMATION_SCHEMA. How is this list populated?
This list is populated based on the schemas used on the endpoint, for example MS SQL. If you right click on an MS SQL table and select Design, it brings you to a page with the different attributes and a properties menu on the side. One of the options in properties is Schema.
The list inside of Connector Xpress only draws from the schemas that are actively in use in your MS SQL instance. So, if you choose a new schema in one of your tables, it will also appear in Connector Xpress.