Hello,
The idea is to pass variables to a child flow.
https://docs.microsoft.com/en-us/power-automate/create-child-flows
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In your image what values are you inserting (Business Unit, Area, Approval Level, Approval Sub Level) to create the child flow? I mean, your flow has no variables- What are you sending there?

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Check my example:
Parent Flow:
Notice you I pass the variables ContactName and ContactEmail (defined in the child flow) as you have done.

Child:
The variables here were requested in the ("Run a Child Flow").

Test:
As you can see, after running the parent flow, the child flow is triggered. The values coming from the parent flow are "populated" in this variables ContactName and ContactEmail.

And I can use them in the rest of the flow. The dynamic reference is coming from the child trigger but the value was imported from the Parent.

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Thank you,
BR