"not understanding how folders could exist inside of other folders" -- My mom is 70 years old now, and I easily get frustrated whenever she's stuck with seemingly simple tasks with her computer. I usually scold her and yell at her, "This is so obvious, how come you don't know?" -- I always regret doing that afterwards. After I'm calm, I ask her why, trying to understand it from her perspective. Every time I do this,…
I have an informal rule that I will try to get someone at my job that has never seen or used the application to be the one to test out new features or UI changes. Generally just asking when they have some time, handing them a phone or laptop, and asking them to do a task in the app (with a small amount of background about the task if needed).
There has never been a case where this hasn't monumentally improved the application. Questions like "what do I do here?", "how do I get it to start?", and "did it work?" were extremely common for quite a while before we managed to get the UI in a good state. You just don't see the implicit assumptions you make at so many places.
Sadly it's hard to "formalize" something like this (at least in my experience), because the benefits seem to be greatly reduced if the person testing has seen or used the application before, and I found it works best the "further away" someone is from software development.