Is there a way to bind eraser mode on to sampling no color, and then turn it off when successfully sampling a color?
Using sample color from layer, if there are no colored pixels at a given point in the layer, the sample tool just keeps the existing color. It would be very convenient if this could instead switch eraser mode on and switch to a "no color" value, and then toggled it back off when successfully sampling a pixel that is coloured. I prefer this method of interface as it keeps all of my color, brush size, drawing, and erasing with the current tool very quickly accessible on the dominant hand.

Is there a way to do this currently in Krita? I tried google, but couldn't find anything on it, probably because it's a rather vague thing to describe to a search engine. But, it's also a rather vague thing to define as a shortcut, and shortcuts in Krita seem to already be fairly restrictive in how they operate, outside of keyboard hotkeys.

I think the short answer is 'no' but a quick press of the 'E' ley (to toggle Eraser mode) with your other hand isn't too difficult? I assume you're using the Ctrl key with your other hand anyway for colour picking.

I map color picker to a pen button, along with brush size, and use brush size and brush erase without relying so heavily on undo.
My left hand is free to stabilize my tablet, or drink coffee, or do whatever it is left hands should be doing.

It might not seem like a lot, but having all the important things mapped to your dominant hand can really improve workflow.

Krita already does reset the eraser flag when you sample a color, so it's just the trigger of sampling nothing in the end. Maybe I can convince a friend to make a plugin script for it.