Export all the invoices I've sent for the past 3 years?

I see that you're seeking assistance with exporting an invoice in QuickBooks Self-Employed (QBSE), alex209. Let me share some insights. 

In QBSE, exporting your invoices as Excel is currently unavailable. I recommend sending feedback so that our team developer might be able to consider including it in the software.

Here:

1. Go to the Assistant icon located at the top right. corner. 
2. In the chat box, type "send feedback."
3. Select Add a feature.
4. Type the topic of your concern. 
5. Send the input, then hit Yes.

However, you can still export it using a PDF file and download the invoices one by one. 

In addition, you can see this article if you want to learn how to get transactions before you connect your accounts:  Add older bank transactions to QuickBooks Self-Employed.

For further inquiries, please enter your concerns for me or us to assist you. I'm always happy to lend a hand.