I have imported the banking transactions manually with a csv file. But, the bank balance shown in the banking function still appear HK$0.00. May I know how to update it?

Your confusion ends here, @info-solacetree-.

Allow me to fill you in on everything you need to know about importing bank transactions in QuickBooks Online (QBO).

Once you import your bank transactions manually, QuickBooks doesn't have access to your bank, which is why the bank balance will appear as zero. Your actual bank balance will only appear if you connect your bank account in QBO. 

If you want to connect your bank account, you can read this article for more guidance: Connect bank and credit card accounts to QuickBooks Online.

Just in case you want to learn how to categorise or match bank transactions in QBO, you can check out this article here.

Should you need any assistance managing your bank transactions in QBO, I'm available here to help any time!