Determining a click region for scroll, simulating the click

Microsoft’s OneDrive website has many pages where the scroll bar doesn’t work with page up/down keys when the page loads: you have to click a region of the page near the scroll bar, then keys start working. (Happens with the landing page, the “On This Day” page, etc.)

I want to write a tampermonkey script that does this click when the page loads. I’ve poked around in DevTools for quite some time trying to figure out what happens/changes when I make this click, and I’m at a loss.

How do I go about watching this work in DevTools? Which view reveals it? Should I be using a different tool? Are there js commands I can run from the console that help me out here?

I’m using the latest Google Chrome browser.

(MRE unavailable for obvious reasons.)