Hey,
Thanks for that information. Do any of the columns include a Gross amount?
You cannot manually adjust the amount that's in the banking section. If you import it as the net value; you have to add it as the net value. This will keep your reconcile correct too. I'd encourage you to speak to your accountant, about what you are required to show in your account.
You can import a list of transactions into a Assett account, or set up a Bank Account to represent the shopify account, record the gross income and the fees as expenses from this shopify account,and then use the transfer or bank deposit feature to take the funds from the shopify account to the current account. This is where an accountant will be best to step in and guide you on the way that's best for your business.