Will Netfile include my Request for Capital Loss Carryback (form T1A)? Or must I mail it separately? There seem to be conflicting older answers on the web.

You do not need to mail anything in with your request for a Capital Loss Carryback. Although the CRA information does say "send in the form", with NetFiled returns nothing is actually "sent" in to CRA, nor is a T1ADJ required to adjust the prior year tax returns. 

You can complete the information in TurboTax by using the "FIND" button, searching for "Losses" and complete the section that asks how much and which year you would like to "carryback" your losses to.

Here's some more information from TurboTax: https://turbotax.intuit.ca/tips/carrying-capital-losses-backward-or-forward-6249

When I create the PDF for 2019 where I've filled in details of capital losses to be carried back clearly shown in Schedule 3 (and I verified the details appear in my T1A in TurboTax), the T1A is NOT included in the PDF. How can I be sure that it's actually being sent to CRA if my copy doesn't include it?

Thanks,

-sg

I was wondering the same thing.  I just found that if you look at your Express Notice of Assessment, you should see a note in it like this:

---

We got your request to carry back a loss to previous years. If we change a previous year's tax return, we will send you a notice of reassessment.