Is there a way to not add the requested item in all carts ? e.g. when I request 400 rails, it will add 400 in each of my 4 carts. I want items be be in a specific cart, is that doable, if so how ?

I think you're using LTN, right? Carriage configuration is individual "normally", but using the new LTN integration, it doesn't have a way to handle having specific carriages in the train handle the requests.

I need to figure out some better methods of managing the configuration of the carriages for LTN users without individually managing each carriage's configuration, but the way you can work around this at the moment is to specifically configure requests in the carriage UI for the station that has the rails - if a carriage has a configuration for a station, it'll ignore what it would normally request via the LTN integration; for the carriage picking up the rails set it to get 400, and for the others have them request something that they'll never get just to have a filler item. Then the big hassle is copying this configuration appropriately among all of the trains that might service the request.. that's the part that gets unreasonable :(

I have LTN installed, but have it not configured for this station. I will checkout several options. Tnx