I would like to be able to adjust the size of multiple strokes at once to add highlights or shadows in my Dore style line art drawings.   Much like a blur brush in GIMP that affects strokes aleady drawn, it instead would thicken or thin the strokes but not the entire stroke, just in the area of the brush.

Is there such an animal in Inkscape?

Have you tried the „Tweak-tool“ already?

Maybe stroke to path, then tweak.

That's the ticket, exactly what I was looking for!

TYVM!