On the "all ears" youtube channel they recently talked about a "loophole" they discovered that allows you to stack many lightning lanes. Here's my understanding of it: 1. If you book a lightning lane, you actually have a 3-hour window during which you can use your lightning lane (2 extra hours after your official return time)
2. An hour after the return time starts, it actually lets you book another lightning lane even if you haven't used the one that "expired".
3. After booking another lightning lane, you can still access the original lightning lane for 2 more hours. So you could have 4 valid lightning lanes booked at this point.
4. Keep repeating this and you could have many lightning lanes booked (in the video they showed having 10 at the same time)
Unlike the genie plus 2-hour window, this window starts after the lightning lane return time, not after the booking time, so at first glance it seems less useful.
But one scenario where I could see this being useful is stacking during a lunch break (or resort nap break). i.e. if I were to take a break for lunch at noon, I could have 3 lightning lanes with return times at noon, and then at 1pm I can book 3 more lightning lanes. I'd have to use the first 3 within the next 2 hours but still have an additional 3 booked for later. If I get very lucky with return times I'd make the second batch of 3 happen at 1pm, so by 2pm I can book another 3. And so on. I wonder if you could also do this first thing in the morning, if you plan to not be at the park for an hour after it opens. Though without using a lightning lane, you're still locked to the tiers, so it would be less useful, if even possible.
Rob did something like this on his recent multi-pass video, where he tapped in at Soarin even though it had expired. I'm not sure if I'd be brave enough to stack them in the way you're describing, I'd always have doubt in my mind that they'll refuse you entry.