You can convert a Subsystem block or Configurable Subsystems block to a Variant Subsystem block.
Right-click the block to and select Subsystem & Model Reference > Convert Subsystem to > Variant Subsystem.
During conversion, Simulink® performs the following operations:
Replaces the Subsystem block with a Variant Subsystem block, preserving ports and connections.
Adds the original subsystem as a variant choice in the Variant Subsystem block.
Overrides the Variant Subsystem block to use the subsystem that was originally the active choice.
Preserves links to libraries. For linked subsystems, Simulink adds the linked subsystem as a variant choice.
Simulink also preserves the subsystem block masks, and it copies the masks to the variant choice.