Prime Select List (deep cascading) fields can be used in JQL. Below are a few useful examples.
Check if the field has any value (or has none)
IS EMPTY and
IS NOT EMPTY can be used to search issues where the field has any value, or none.
Search values containing a specific text
~ can be used to search issues where the field has a value containing a specific text.
Search by leaf value
Values can have multiple levels, for example “Vehicle”, “Car” and then “Mercedes”. The search alias
LeafValue can be used to only consider the lowest level i.e. the leaf when searching for issues:
Search by full value
The search alias
FullValue can be used to consider all the levels when searching for issues: