Subsystem Instance
The Subsystem Instance () feature represents an instance of a subsystem defined by a Subsystem Definition feature.
Name
Enter a component Name for the subsystem instance. The default name (for the first instance) is X1.
Node Connections
Select the Name of subsystem link from the list of defined subsystems in the model and set the Node names at which the subsystem instance connects to the main system or to another subsystem.
Input Parameters
Set the values of the parameters in the Expression column to be used by a subsystem. This is an optional feature and enabled only with the Advanced Physics Options selected. The parameters are shown in the list only when a subsystem chosen in the Name of the subsystem link defines any parameter. The values of parameters provided at this node override the default values of the parameters specified at the Subsystem Definition node.
Context Menus
Ribbon
Physics tab with  Lumped Mechanical System selected: