Transport Expresso has the ability to be able to create a transport form and create/assign a task within the SAP GUI when the transport is released or when objects are attached to a transport.
This then avoids the need to login to Transport Expresso to create the transport forms and the approval process is then started as normal. All custom fields and user exits are processed as normal and access to this is controlled via the TE authorisations.
Transport form creation screen in the SAP GUI:
Task screen in the SAP GUI: