Creating Assignment Category Sync Rule for Job Selection in Redwood

Summary:

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Hi all,
I am working on Request a New Position and we have a requirement that when select a job , Assignment category on position page have the same value of assignment category of selected job .
I am trying to create the same rule as business rule but couldn't find related jobs fields !
Kindly note that we created this rule with Autocomplete as Field Modification Rule and sandbox was published but after moving to Redwood it was gone.
So , How we can create the same rule in Redwood ?

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