Blue marker is missing on making changes in Blend Distance in prefab of Density Volume

Steps to Reproduce:

1. Create a new Project with 3D Template
2. Open Package Manager window
3. Find High Definition RP and click install
4. In Project window right mouse click > Create > Rendering > High Definition Render Pipeline Asset
5.Open Project Settings > Graphics > Scriptable Render Pipeline Settings slot > Drag and drop HDRP Asset to this slot
6. Create an empty Game Object
7. Add Density Volume component to it
8. Make prefab of this GameObject
9. Change value Hierarchy > GameObject > Inspector > Density Volume > Blend Distance > X = 2, Y=2, Z =0

Expected Result:
Blue margin line appears on changed values

Actual Result:
Blue margin line is missing

Reproducible on: 2020.1.0a10, 2019.3.0b8, 2019.3.0b4

Environment: Windows 10 and Mac 10.14