There are more questions in this thread than answers, so I thought I'd share what I've learned. I'm a Canadian citizen living and working in the USA so I'm a non-resident. I'm also not a tax expert so take everything below with a grain of salt. 🙃
First, you can call the CRA at a special line (for some reason I can't post the phone number here?) and talk specifically to someone about non-resident withholding. I was able to get through without any wait, which was a pleasant surprise. The person was very helpful and explained quite a bit.
What I learned after talking to the CRA agent is that the NR-4 is essentially a "mini return", filed by the company that issues the funds to you and submits the tax to the government on your behalf. It tells the CRA as a non-resident you've earned income, and that taxes have been paid. The reason why there's no place to "put the NR-4 into TurboTax" (which is what I too was trying to do) is that there's no need to do it unless you are also trying to do a full return. If you only have the NR-4, and no other Canadian income or losses, my understanding is that you do not need to file a return.
Now things get a little more complex if you have losses (I have a T5013 with losses) and you want to get back some of the tax you paid on the NR-4. If you don't put the info from the NR-4 into TurboTax, it doesn't know you've paid taxes, therefore there's nothing to get a refund against for the loss. That's something I'm trying to figure out now and will report back here if I get clarity.
