It isn't looking promising. This is from the TestStand help:
With the exception of substeps named OnNewStep, TestStand does not call custom substeps. Use the TestStand API to invoke a custom substep from a code module or user interface. You can create a custom substep named OnNewStep for TestStand to call each time you create a new step of that type. For example, the built-in If step type uses an OnNewStep substep to insert a matching End step.
TestStand already creates a unique ID when copying and pasting steps. Did you need to assign a specific one?