documentclass[margin=1cm]{standalone}

usepackage{tikz,pgfkeys}
usetikzlibrary{calc}

pgfkeys{
    /absolutenode/.is family, /absolutenode,
    default/.style = {},
    position/.store in = position,
}

newcommandabsolutenode[2][]{%
    pgfkeys{/absolutenode, default, #1}%
    tikz[remember picture,overlay,x=paperwidth,y=paperheight]{%
        node[anchor=center,inner sep=0pt] at ($(current page.south west)+position$) {#2};
    }
}

begin{document}
    absolutenode[position=(0.5,0.5)]{Test}
end{document}