Context: I work in an office in a semi-private cubicle. People walking past is about the only time people can glance at what you're doing.

It's a fairly relaxed atmosphere, other coworkers who've been here for 15-20 years are doing all manner of things when they're not working on work: looking for new houses, listening to podcasts, etc. I can have headphones in and I have total access to my phone, on my wireless network, not WiFi, but that doesn't really matter honestly.

I want to make better use of my time besides twiddling my thumbs or looking at news articles.

What sorts of things can I do to earn a little supplemental income. I was honestly thinking of trying stock trading, but I know nothing about it so it would be a slow learning process.

It would have to be a drop-in-drop-out kind of activity, something you can put down at a moments notice in case I need to respond to customers/emails, my actual job comes first after all.

I'm not at all concerned with my current income, I make enough to live on comfortably with plenty extra to save and spend on fun, I just want to be more efficient with my time, you know?

PSA: don't bother with "talk to your boss about what other responsibilities you can take on with this extra time to impress them etc." Just don't bother.