Steps to reproduce:

1. Create new project.
2. Create several scenes.
3. Open those scenes in additive.

things that does not work are listed below.:
4. Reorder scenes, press undo
5. Unload/Load scenes, press undo
6. Open/Remove scenes, press undo
7. Open scene set, press undo
8. Set other scene as active, press undo

Result: none of those operations above does not seem to have undo

Reproduced on: 5.5.0b5, 5.4.1p2