Thanks for your prompt reply, Chipndale.

You have the option to manually delete the refund/payment in the Payments tab. 

To record the 2 sums of payment/refund with different dates for F5 & F7, here's how:

1. Go to Taxes > Payments.
2. Click the Record payment button.
3. Add the payment details and click Save.

For recording a refund, go to the Returns tab and under the Filed returns section, select the View summary drop-down menu and choose Record refund. I've got this sample screenshot for a visual reference:

I've got this article for more details: File your GST return and record tax payment in QuickBooks Online.

Please let me know if you have any follow-up questions or other concerns. I'll be around to help you out again. Take care!