I wanted to see my 1040SR. Printed my return to mail-in. Found many errors. Need to start over. No "Tax Tools". How do I delete my return that I already printed?

If you're using Online TurboTax, I suspect you've already paid since you were able to print the return.  If so, you won't be able to start over if you already paid, but below I'll tell you how to open it up and edit it.   

I'll also tell you below why you are not seeing TAX TOOLS and how to get back into your return.

However, if you have already paid for the product, you can't start over, but you can go back in and make all the corrections you need to.   Source:

FAQ:  How do I clear and start over in TurboTax Online?

https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-clear-and-start-over-in-turbotax-onli...

If TurboTax thinks you were finished, and thus your return is closed, you won't see the full left column menu  until you open the interview back up.   Here's how to open it back up to make the corrections.  

•  Log in and at the Tax Home look for a link "Add a State".    That doesn't really add one.  It just opens the return interview back up.