From OmniStudio Best Practices for Modular Script Design, OmniScript Actions are the preferred mechanism to invoke another OmniScript within a parent OmniScript. This approach enables reusability and modularization, especially when a function (like updating billing information) is common across many interactions.

A. OmniScript Action – This is the correct and standard method for embedding or launching one OmniScript from another. It allows developers to reuse common scripts without duplicating logic.

Incorrect Options:

B. Custom Action requires custom Apex or LWC development, which is unnecessary for this use case.

C. Lightning Action is typically used to invoke OmniScripts from Lightning pages, not within OmniScripts themselves.

OmniStudio Developer Guide → OmniScript Actions