In QuickBooks Sole Trader, the ability to edit invoice or estimate templates directly isn't available, Jake67.
However, you can still personalise your invoices and estimates by navigating to the Manage section next to Record payment, where you can explore available features such as Customization, Payment Options, and Design Scheduling options.

Please note that the full template editing feature is exclusive to QuickBooks Online plans Advanced, Essentials, Plus, and Simple Start.
If you need guidance on personalizing invoices within QuickBooks Sole Trader, feel free to ask. We're here to help.