Thanks the idea from:  The_laziest_engineer (Printables) (Makerworld)

I redesigned the switch part so that the train can pass through from both directions, regardless of the switch’s position.
To make it work, you'll need a transparent silicone hair tie (0.6in / 1.5cm), which you can find at any health and beauty store like DM, Müller or Rossmann. (or Temu/Aliexpress)