So i want to make building sytem that allows me to build train track in game, connect them and later place train on them so that i can travel/transport objects with it.
hmm so create a building system then. it shouldnt be much different than building foundations. u just snap one foundation to another. if you know how to use ue4 well enough u can build the system yourself or just try searching up a tutorial.
You can create several rail track BPs (straight, turnning, intersection, switches) and add splines to them. You can use the splines for trains movement, and I believe you can use splines’ extreme points to snap tracks to each other. If not, you can always add soskets to tracks meshes.
what you need can be easily achieved with splines and then move an object (in your case the train) along its path.
there is a rollercoaster plugin already available open source that you can have a look at