Cannot drag and drop to add an element into array

Unity 2022.3 (also 2021.3 i think)

- Create several BooleanActions.
- Inspect one of the BooleanAction.
- Drag another BooleanAction into the current one's Sources array header
- expected behaviour: that other BooleanAction is added into the Sources array
- current behaviour: it is not added
- guessed reason: Sources array is List

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- Create TrackedAlias and inspect it
- Create a camera rig (e.g. oculus intergration camera rig)
- Drag the camera rig into TrackedAlias Camera Rigs array header
- observed the rig is added into the array
- guessed reason: CameraRigs is derived from ObservableList