Sequencer: Expansion State of Animation Track Properties is not saved

The expansion state of Animation Track properties is only saved when Section > Advanced is expanded or collapsed.`

1. Add a Skeletal Mesh to the Sequencer and add an Animation Track with any animation.
2. Right-click the Animation Track to open the context menu.
3. Expand Animation > Playback in the context menu.
4. Click outside the context menu to close the popup.
5. Right-click again to reopen the context menu and check the properties.
6. Confirm that Playback is now in a collapsed state.
7. Expand Playback again, then also expand Section > Advanced.
8. Close the context menu and reopen it.
9. Confirm that the expansion state of Playback is restored.