When you enable the multi currency feature and change your home currency, any previous transactions with the old currency will remain the same. You will need to convert those transactions manually or purchase a third-party service to do so.

Hello there, jacko2.

I can see a similar post from another thread, and my colleague has answered your post. 

You can refer to this link: https://quickbooks.intuit.com/learn-support/global/other-questions/multi-currency/01/1128000#M3443.

Know that the Community is always here to help.