Hi michelle@brodeur,
Welcome to the Community. It's important to correctly record your transactions to keep your books balanced. QuickBooks Online is a great program that gives you the ability to easily track your sales and expenses. I'd be glad to help.
At this time, the program doesn't allow using the GST payable liability account when adding a transaction from the bank feed. You can use a journal entry to enter your transaction in the GST Payable liability account. If you track your sales tax in QuickBooks Online, I encourage you to review this article.
Let me know if you have questions, I'll be happy to help.