Add the following expression to evaluate both options of a Select List (cascading) custom field.
%{issue.cfaaaaa} = "Parent option - Child option"
Please, replace the ID of the field code before testing the expression and note that the parent option must be separated from the child option with a hyphen "-" surrounded by two spaces.
By adding .0 or .1 to the field code of the custom field, the respective values of the parent option and child option can be accessed.