I figured it out.
Though the resolution dropdown’s list maxes out at 1200, you can just type in higher numbers, and it scans at those higher numbers. I tried 2400 and 4800 and verifed that I got higher resolution files. The 4800dpi one is pretty amazing.
It will only allow scanning relatively small areas with such high resolution; it seems to have a max file size or something. At 1200 I’m able to scan an entire old children’s book illustration; the scan is 7184 x 4777, 6″ x 4″, and 34MB.
At 2400 I had to zoom in on one character in the illustration. That scan is 4160 x 5912, 1.7″ x 2.5″, and 24MB.
At 4800 I had to zoom further in on the character, excluding some wave lines (it’s a beaver sitting on his lodge which I use on the title page of my Kindle books; yes it’s public domain). That scan is 5295 x 9586, 1.1″ x 2″, and 50.76MB. Not much bigger than a typical postage stamp.
At 4800, I think it must be interpolating for one dimension from the max stated in the specs which is 2400 x 4800. When I zoom way in I can see how one dimension has much better gradation of grays than the other dimension.
Googling the error I got when exceeding its max output size, I don’t see any posts later than about the time I bought this scanner in 2013. Fingers crossed that means later Canoscan LiDE models can handle larger files and therefore larger scans. After the 110 was the 220, then the 300/400 which are current, released in 2018.