Steps to reproduce (or look at the attached image):
1. Create a new Unity project
2. Select any object in the Hierarchy
3. Add 'Timeline' to that object via Timeline Editor window
4. Keep adding 'New Track's' until there's no empty space left in the Track GUI (notice that you can create new track by right clicking the Track GUI)
5. Scroll to the bottom of the tracks

Actual result: There's no gap to right click and add new Track OR 'Add Track' button on the bottom of the 'Tracks' GUI
Expected behavior: there's a little gap left at the bottom of the tracks for user to right click OR there's a 'Add Track' button in the bottom of Track GUI(like in inspector/animation windows)

Reproducible with: 2017.1.0p3, 2017.2.0b5, 2017.3.0a2