how to configure the network so that, having an example:
1.)
in the depot train with 1 wagon, in which only 10-15 slots are free. I understand that it is not true to transport excess freight on the train

How to take this into account for auto-building a route?
in my situation the train leaves for the station to provide more resources for loading than there are slots in the wagon.
(I see it this way:
during the parking of the train in the depot, it is necessary to transmit a signal about the contents of the entire train to the loader station. and there with the help of arithmetic combiners determine the amount of free space on the train.
but even if it does, I do not want to pull long wires between all the stations.)
2.)
Is it possible to build more complex routes?
based on again empty slots in the wagon.
example:
-> depot
-> pick. iron ore 20k from station 1
+ take copper ore 30k from station 2.
-> un-load: iron ore to station 1.1. and unload copper ore on station 1.2
P.S. I understand that I can use several trains

p.s. sorry for my english