@martyn_thomas I updated my post above. You are on the right track. It misses one rule to restore display when there is no sub-category. (basically, the solution is to hide always the first element and unset the second)
@martyn_thomas I updated my post above. You are on the right track. It misses one rule to restore display when there is no sub-category. (basically, the solution is to hide always the first element and unset the second)