M785 lever blade on M6100 master cylinder

Would the above work? They look very similar but I don’t want to pull everything apart to find out it doesn’t work.

Background is that I have Deore M6120 brakes but would like tool free reach adjust, I have a set of M785’s on a pub bike and I’d be happy to swap levers if it’s possible. I really like the Deore 4 pots but needing an Allen key is a bit annoying.

Why not just swap the full lever over

Because the old lever doesn’t have the extra brace of the new lever so doesn’t offer quite as firm of a bite. And I don’t like the shiny silver on the old XT ones…

https://si.shimano.com/en/

Chech the tech docs and compatibility maps

How many times do you need the reach adjust on the trail? I’m a set and forget type

Not a lot but a couple of days at Dyfi had me needing to adjust it a bit and I’m quite picky about lever reach. Also if you advance the pistons to reduce free stroke then it eventually goes back to normal which usually requires adjusting reach as wheel removal isn’t ideal mid ride.