

The main reason why few trailers do not allow you to connect two trailers after the tractors is due to international law that say there is a max length and total weight that you are not allowed to extend. YOU CAN drive with 3-4-5 trailers BUT only on private property and not on public road. You can however specificly ask for such extention to be installed on your new trailer in some cases but it will cost extra and might not be avaliable anyway. Reason why not all trailers can pull example two trailers after each other is basicly due to how it was designed by the manufactor since not all people have such a demand or need. ( farmer who is an expert in machines and plants ) I am a real life Heavy machiner operator.

The drawback to the trailers with a front steering axle is that they are much harder to back up and have them go where you want, but you need the front steering axle for the extra trailers in a train. What you could also do, if you don't want the front trailer to have the steering axle is use a trailer with a ball hitch, like this one for the front trailer. You can see in the pics how they attach together. This one is just the trailers with the a-frame tongue and front steering axle. There are many others and you can mix & match the manufacturers, so these are just examples of what you can find in game. These are mods on the in-game mod hub and they illustrate what you're looking for in trailers. Maybe the best way to explain is to show: There aren't adapters, they're separate trailers and you need to make sure when you buy them that they do have the hitch attached to the back.
