Crin's graph tool, squig.link and others support a few targets by default (right below the chart) like Harman targets, IEF Neutral, Diffuse Field, etc. Select your headphones, your target of choice, press the AutoEQ button, and the tool will generate EQ parameters. Afterwards you can even tweak the generated EQ params and see the resulting frequency response curve (typical use-case is if you want more bass for example). This works really well. But if you want to use your own custom target, it looks like you need to use the actual AutoEq tool written in Python... I've never done this though. Actually the graph tools have an "Upload Target" button in the "Equalizer" tab which looks like it can be used for custom targets.

Edit: apparently you can also select another headphones' frequency response as a target. Nice!