Stack By Quality - Vanilla-Expanded/VanillaExpandedFramework GitHub Wiki
CompProperties_StackByQuality makes items only stack if their qualities are the same.
It is a comp class, so you just add it in XML in the <comps>
tag. For example, this is used in Vanilla Cooking Expanded to avoid cheese of different qualities stacking, and thus "ruining" the higher quality.
<comps>
<li Class="VEF.Cooking.CompProperties_StackByQuality"/>
</comps>