I remembered that there is a non-toxic pre-emergent: it's called corn gluten. That's good news because it means that next year you can apply it and the crabgrass will not come back. Corn gluten also prevents a lot of other weeds like dandelions. I know you're an expert searcher, so check it out. IIRC, it has to be applied very early, so check for that in your reading, should you decide to read up on it.
Now the only problem that remains is getting it out of that section of your lawn.
I checked out another solution, but if you recall I said I was pretty sure you wouldn't like it.
The solution is a robotic mower. My thinking was that you could get one of the less expensive ones and set it up to do an extra cut during the week so the crab grass doesn't stand out.
A robotic mower can even be built. Don't know if gs has a propensity for that sort of thing, but there is info on it at youtube. Also Reddit has a whole sub-Reddit on robotic lawnmowers.
I'm thinking of suggesting my funder get a grant to get a robot lawnmower because the facilities dept at the school is a miserable failure. They keep running over my expensive metal watering hoses. They also leave the gates open when they leave, thinking that the school's maintenance dept will close them, but often enough, they don't. Thus anyone can walk in and grab a tomato or two, not something my hardworking community gardeners want to see happen.
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