If you just created a subsystem, you may be able to undo the step. Under the edit menu, select Undo Create Subsystem, if available. Otherwise, follow these instructions.
To ungroup a subsystem
In the model workspace, double-click a subsystem.
Draw a box around the components in the subsystem.
Cut or copy your selection.
From the Model Workspace toolbar, select Parent (
) to navigate up one level from the current element.
Paste your selection back into the model workspace.
Delete the original subsystem.
Grouping Modeling Components into Subsystems
Model Workspace Toolbar
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