Reproduction steps:
1. Open the attached project "AnimationProperty.zip"
2. In the Project window under the "Scenes" folder open "Menu.unity"
2. In the Hierarchy window under "CanvasStart" GameObject select "Start" GameObject
3. In the Inspector window make sure that Outline component is above of Shadow component in the ordering
4. Open the Animation window with "CTRL + 6" shortcut
5. Press "Add Property"

Expected result: Outline component does not replace Shadow component in Animation window property selection
Actual result: Outline component replaces Shadow component in Animation window property selection (See attached "AnimationProperty.mp4")

Reproduces on: 2018.4.23f1, 2019.3.15f1, 2020.1.0b10, 2020.2.0a12

Notes:
-Reproduces on a new project