SC2Mapster

I found the function I needed. It is UnitCargoGroup(unit: Unit): UnitGroup

And this is the iteration I use to accumulate the army value of the units inside Nydus Networks:

                ------- Units inside nydus networks are not included in the `Entire Map` region. So their upkeep is treated sepparately here.
                ForEachUnitInGroup(nydusNetwork,(UnitGroup("NydusNetwork",player,(RegionEntireMap()),Excluded: Dead,1)))
                    actions
                        ForEachUnitInGroup(armyUnit,(UnitCargoGroup(nydusNetwork)))
                            actions
                                addUnitCost(armyUnit,costAccums[player])

Now the mod calculates the army value correctly.

Thank you MaskedImposer for mentioning the word "cargo". It helped me to find the function I needed.