Simply put, when hovering over a Part category in the build menu, there should be an option for modders to put an optional description in the tooltip, for the purposes of explaining lore around the part group or giving a brief description on the types of parts found in there. An example of how this could be implemented:
AntimatterParts
{
NameKey = "EditorGroups/Antimatter"
TooltipKey = "EditorGroups/AntimatterTooltip"
Icon
{
Texture = "gui/group_antimatter.png"
}
}
