  The diagram depicting the abundance ratios [Mg/Mn] vs. [Al/Fe] has gained
attention in recent literature as a valuable tool for exploring fundamental
aspects of the evolution of the Milky Way and the Local Group. In particular,
this combination of elements is supposed to be highly sensitive to the star
formation history (SFH), unveiled by the imprints left on those abundances.
Unfortunately, a complete discussion on the uncertainties associated is still
missing, making it difficult to know how reliable the associated results are.
In this paper we analyze, by means of detailed chemical evolution models, the
nuclear uncertainties of Mg, Al, Mn and Fe to show how different yields can
affect the trends in the [Mg/Mn] vs. [Al/Fe] plane. In fact, if different yield
assumptions produce conflicting results, then the [Mg/Mn] vs. [Al/Fe] diagram
does not represent a strong diagnostic for the SFH of a galaxy. We discuss the
results on the [Mg/Mn] vs. [Al/Fe] diagram, as predicted by several Milky Way
(MW) and Large Magellanic Cloud (LMC) chemical evolution models adopting
different nucleosynthesis prescriptions. The results show that the literature
yields require some corrective factors to reproduce the APOGEE DR17 abundances
of Mg, Al and Mn in the MW and that the same factors can also improve the
results for the LMC. In particular, we show that by modifying the massive stars
yields of Mg and Al the behaviour of the [Mg/Mn] vs. [Al/Fe] plot changes
substantially. In conclusion, by changing the yields within their error bars,
one obtains trends which differ strongly, making it difficult to draw any
reliable conclusion on the SFH of galaxies. The proposed diagram is therefore
uncertain from a theoretical point of view and it could represent a good
diagnostic for SFH if the uncertainties on the nucleosynthesis of these
elements (Mg, Mn, Al and Fe) could be reduced by future stellar calculations.
