[semlar]

Sorry, I meant to hook the metatable, let me edit that. It should work for every action button, however it won't do anything until their SetAttribute method is called, so they need to be hidden initially and then this is just to fix it if it changes later.

Alternatively you could try just outright setting the alpha of every texture to 0.. the textures don't appear to be named so you have to loop over button:GetRegions().

You're going to have to fine-tune this to only hide what you want hidden but something like this and then maybe check if the texture path contains UI-QuickSlot..

local function ActuallyHideGrid(barName)
    for i=1, NUM_MULTIBAR_BUTTONS do
        local button = _G[barName.."Button"..i]
        button:SetAttribute("showgrid",0)
        for i,region in pairs({button:GetRegions()}) do
            if region.GetTexture and region:GetTexture() then
                region:SetAlpha(0)
            end
        end
    end
end
ActuallyHideGrid("MultiBarBottomLeft")
ActuallyHideGrid("MultiBarBottomRight")
ActuallyHideGrid("MultiBarRight")
ActuallyHideGrid("MultiBarLeft")