How to reproduce:
1. Open the attached Project "TestProject"
2. In the Project Window select "Assets/ChildSO"
3. In the Inspector Window right-click either an element in the "Items" List, or the "Dummy 1" variable
Expected result: the context menu contains an entry from ContextMenuItem
Actual result: the context menu does not contain any custom entries
Reproducible with: 2020.3.46f1, 2021.3.20f1, 2022.2.9f1, 2023.1.0b6, 2023.2.0a4
Notes:
- The issue also reproduces with child MonoBehaviours
- ContextMenu correctly gets inherited by the child class
- ContextMenuItem does not see methods from a parent class