Instead of setting these inputs as node names, add them as a separate variable in the nodes table. Then, pass them to the plotting function as node labels:
G = digraph(s, t, w, , 'omitselfloops');
G.Nodes.Label = n;
plot(G, 'NodeLabel', G.Nodes.Label);
The node names of a graph have to be unique because they can be used to specify a node as input to some functions (for example shortestpath). But this is not the case for the labels in the plot of a graph.