On dragging the mouse cursor over the input field of the following properties don't change its value in the Skinning Editor.
Properties:
Geometry: Outline Detail, Alpha Tolerance, Subdivide,
Weight Slider: Vertex Weight(Bone)
Weight Brush: Hardness, Step
Visibility: Bone and Visibility slider, Refer to the attached video.

Steps to repro:
1. Create a new project with a 2D Template
2. Project > Create > 2D > Sprite > Square
3. Inspector >Sprite Editor > Skinning Editor
4. Create a bone and generate geometry
5. Select Auto Geometry > Change the input value of Outline Detail, Alpha Tolerance, Subdivide

Actual Result: Mouse dragger is missing for all properties in the skinning editor

Expected result: Input value of properties are change using mouse dragger

Note: 2D Animation package is introduced in 2019.3.0b1 with package version 3.0.3

Reproducible in:
2021.1.0a7, 2020.2.0b13, 2020.1.15f1, 2019.4.14f1, 2019.3.12f1, 2019.3.0b1 with Package Version 3.0.3, 3.1.0, 4.0.0, 4.2.6, 5.0.2, 5.0.3

Environment:
Windows10 and macOS 10.15