Why would you need to plot it on a graph?
If you know all the weights and all the arms, you know the final CG.
If you know the CG envelope, you can say yes or no, in or out.
BTW, I've thought many times of doing this myself too. We have to put total weight + cg + fwd cg limit + aft cg limit on our manifests. All of these can be got without using an actual graph.