Hi there,
Glad to have you reach out in the Community. QuickBooks is designed to help you streamline your work and I'll be happy to point you in the right direction so you can achieve your goals.
The ability to subtotal line items on an estimate isn't available. I can see the benefit of having this function and I recommend sending this as feedback to our engineers. You can send feedback by clicking the Gear icon and navigating to Feedback. In the meantime, I recommend looking into third-party apps that can help you with this. You're more than welcome to search for third-party apps on our site using this link here.
Let me know if this info helps. I'll be on standby in case you need anything else.
