What is the best way to set up a 'dummy' account to track my forex trading transactions made in my trading account?

You can set up an asset account for your forex trading transaction,gferguson1815. Let me guide you in setting this up in QuickBooks.

An asset account will track the value and depreciation of your assets. If you already have an asset account set up that matches the description, you can use it. If you haven't set up an account, you can create one. Let me guide you on how:

1. Go to the Gear icon and select Chart of Accounts.
2. Select New.
3. In the Name field, enter the name of the account.
4. In the Account type ▼ dropdown, choose Current assets or Non-current assets.
5. In the Detail type ▼ dropdown, select the option that closely describes the asset.
6. In the Balance field, enter the opening balance amount. Then, select the starting date in the as of field. The balance can be GBP 0.
7. Click Save and Close.

For more details, see this article: Set up an asset account in QuickBooks Online.

Upon sharing the steps above, I'd still suggest contacting your accountant. They can guide you through the process to ensure your books are accurate. You can also find one by checking out this article: Find an accountant or bookkeeper.

Also, I'm adding this article that will guide you in recording asset depreciation and how to reconcile your account in QuickBooks: 

• Record and depreciate assets
• Reconcile an account in QuickBooks Online

Let me know if you have follow-up questions about setting up a dummy account or anything else in the comment section below. I'm more than willing to help. Take care always.