Restrict values in Profile DFF on basis of selected Competency

Summary:

Customer wants to restrict values in DFF based on the selected Competency

Content (please ensure you mask any confidential information):

We have created a content section on Person Type profile using the Competency template. A DFF named 'Evidence' has been created in the same section linked to a value set. The value set contains 4 values (Incident, Training, Exercise, Simulation).

Customer requirement:
When employee selects Competency = Incident Command
Evidence DFF should display only 2 values out of the 4 - Incident, Exercise

For all other competencies, Evidence DFF should display all 4 values.

We are aware on how to create value set values being dependent on another DFF's value set. However, we are unsure what variable/process to use to get the selected Competency value at runtime and use that to restrict DFF values. Can you please suggest a possible solution? We are happy to change the configuration/value set against the 'Evidence' DFF if need be.