I made an example of a hierarchy with buses, and posted in:
Your graphical presentation of a transmission line does not mean anything to KiCad. I don’t have much experience in this area, but I think that creating a netclass for controlled impedance tracks is a much better option. In KiCad you can also assign a wire width and color based on netclass (In Schematic Editor / File / Schematic Setup / Project / Net Classes) and in the PCB editor you can then assign a special track width and clearance to this controlled impedance netclass.