How to make the Functional Area list dependent on the Issue Type value?
Unfortunately, there is no relationship that ties the Functional Area list items to Issue Types to achieve what you described. But you definitely can do it with a “Flex Field”. You’ll just need to create a table that defines that relationship, and name it as the prompt view in the Flex Field configuration. Also, I suggest that you make it a “required” Flex Field, then it will be shown on the Help Desk version of the Issue page – otherwise it will be hidden.