In "Secondary Textures", Zoom in/out slider doesn't scale, and it's not visible.

Steps to repro:
1. Create a new 2D Project.
2. Import a .png file and change the Texture Type to Sprite
3. Sprite Editor > Secondary Textures
4. Move the Zoom in/out Slider.

Actual Result: Slider value doesn't affect on sprite image and it always in a hidden state

Expected Result: On changing the value from the slider, Image gets a zoom in/out

Occurring on: 2020.1.0a10, 2019.3.0b8, 2019.2.0a12

Note: The feature is introduced in 2019.2.0a12

Environment:
Windows 10, macOS 10.14 & Linux