Very briefly, what you should do is use "factors = s.get_decomposition_factors()", to produce a spectrum image, "factors.set_signal_type('EDSTEM')" to pretend that this is an EDS spectrum image, and "factors.add_elements()" to add the elements. Then use "factors.plot(True)" to plot with the lines.
You'll lose the ability to sync the factor and loading plots, but you can get and plot the loadings alongside this with "s.get_decomposition_loadings().plot()".
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or email back here. The former is faster :)