Description
Sub connections are used to share properties between groups of sessions (e.g. the host name). They're also used to regroup many connection types in one computer (e.g. the RDP/FTP/HTTP connection).
Sub connections are configured in the parent connection inside the Sub Connections tab page. Use the predefined variables in the child session to get access to the parent settings. The most common usage is to reuse the host name from the parent within the sub connections.

Sub connections tab page