\startluacode

    local kerns = {
        ["TeXGyrePagellaMath-Regular"] = {
            [0x1D449] = { bottomright = { { kern = -200 } } }, -- math italic V
            [0x1D44A] = { bottomright = { { kern = -100 } } }, -- math italic W
        }
    }

    local function addkerns(tfmdata)
        if tfmdata.mathparameters then
            local kerns = kerns[tfmdata.properties.fontname]
            if kerns then
                local characters = tfmdata.characters
                for unicode, specification in pairs(kerns) do
                    local character = characters[unicode]
                    if character and not character.mathkerns then
                        character.mathkerns = specification
                    end
                end
            end
        end
    end

    fonts.handlers.otf.features.register {
        name         = "mathkerns",
        description  = "additional math kerns",
        default      = true,
        initializers = {
            position = 1,
            base     = addkerns,
            node     = addkerns,
        }
    }

\stopluacode

\setupbodyfont[pagella] \showglyphs

\starttext

    Don't use this method in \ConTeXt\ as we have
    other mechanisms for it!

    \startformula V^i_j = W^i_j \stopformula

    \page

    \typefile{kerns-002.tex}

\stoptext
