Simple Computer Aided Railway Modeller

Click with right mouse button over the name of currently selected library (located on top of the track selection panel) - a list with libraries will appear.

Note If you do not see your preferred scale or track producer in the libraries menu, go to "Tools" > "Settings" > "Tracks Panel" and ensure that the required scale has a check-mark in "Selected scales" list and the "Libraries list sorting" is set according to your needs.