Currency Issues

[Les]

Several days ago, I wrote to this list concerning problems regarding
exchange rates. (copy of email below).

In that email, I used terms such as folders and I should have used
accounts and sub-accounts.  But the facts are still the same. 

Could someone please assist in solving this problem?

Thanks,
Les

I have a bank with multiple currencies.  The primary currency for this
bank is HKD.  Within this account I have a folder "saving" and type is
cash.  Under "saving" is a folder "currency" with type cash and contains
several other folders: CNY, HKD, etc

Everything works fine except CNY does not roll up properly (it does not
maintain an exchange rate for CNY:HKD).  Is there a way to solve this? 
Using LMDE v 1403 and GC 2.4.13.