Aim section Property Gizmos are disappearing on adding any extension, On hovering mouse on Game view, it appears.
-Tracked Object Offset.
-Screen X.
-Screen Y.
-Dead Zone Width.
-Dead Zone Height.
-Soft Zone Width.
-Bias X.
-Bias Y.

Steps to repro:
1. Create a new project.
2. Window > Package Manager > Cinemachine(2.6.0-preview.5) > Install.
3. Cinemachine menu > Virtual Camera.
4. Create a Cube game object and Assign to "Follow" & "Look At" property of Virtual Camera.
5. Virtual Camera > Extension > Add Extension > Cinemachine Camera Offset.

Actual Result:
Aim section Property Gizmos are disappearing on adding any extension

Expected Result:
Aim section Property Gizmos should not disappear on adding any extension.

Reproducible in:
2020.2.0a13, 2020.2.0a1 with Package version 2.6.0-preview.5, 2.6.0-preview.3

Working Fine in:
2020.2.0a13 with package Version: 2.6.0-preview.2, 2.5.0.
2020.1.0b11 with package Version: 2.6.0-preview.5, 2.5.0.

Environment:
Occurring on Windows 10 & Mac 10.15.