Reproduction steps:
1. Open the user's attached project "Spielwiese 2020.zip"
2. In the Project window navigate to "Assets/Modules/GetALife/Scenes" folder and open "GAL-test.unity" Scene
3. In the Hierarchy window navigate to and select the "Template/DetailWork/LPStraightVertical (2)/BG/rightBorder/rightBorder" GameObject
4. In the Inspector window under the Sprite Shape Controller Component press "Edit Spline"
5. In the Scene View select the bottom point and create a new Spline pivot point

Expected result: Sprite Variant Window appears in Sprite Shape Controller Component when selecting a Spline pivot point
Actual result: Sprite Variant Window does not appear in Sprite Shape Controller Component when selecting a Spline pivot point (See attached SpriteShape.mp4)

Reproduces on: 2D SpriteShape 3.0.12 (2019.4.7f1),2D SpriteShape 4.12.0 (2020.1.1f1),2D SpriteShape 5.0.0 (2020.2.0a20)
Could not test on 2018.4 due to the project breaking when downgrading

Notes:
-In 2D SpriteShape 5.0.0 the Sprite Variants in the Sprite Variant window appear completely white
-Sprite Variant window appears correctly if another GameObject is selected while a Spline pivot point is being edited
-Issue occurs when a new Spline pivot point is created when the bottom point is selected beforehand