[Harven]

You can try iterting through the tooltip childs like that:

local function CheckChildren(control)
    for i=1, control:GetNumChildren() do
        local c = control:GetChild(i)
        if c then
            local type = c:GetType()
            --do something, like GetText if the control is a CT_LABEL
            CheckChildren(c)
        end
    end
end
 
CheckChildren(PopupTooltip)

But if I remember correctly you will get nothing, like the controls in tooltips are some kind of special control filled by the client.