unfortunately Giants game engine only allows items to be connected in one direction, meaning you cant build a train from one end, then run around it and connect to the other side.. the only way to do this is to disconnect all of the railcars from each other by holding control and hitting the disconnect button, then running around and connecting them all back together from the other end. Nothing I can do to change that sadly as its a limit of Farming Sim. Is that what you are trying to do?
Yeah I recently did this while switching out an industry off of the mainline, then I used a passing siding to run around the train and grab it from the other end. Unfortunately this is the only way that you can do it as I described it, with disconnecting all the railcars and then reconnecting. I was on flat ground so it wasnt a huge deal as nothing moved, but it definitely breaks the emersion having to do that :/ I am glad you are enjoying it tho! I have plans for another update this weekend!