How to reproduce:
1. Open the attached '1291455.zip' project
2. Open 'SampleScene' (Scenes > SampleScene)
3. Open Window > Sequencing > Timeline
4. In the Project window select the 'Test' Timeline Asset (Assets > Test)
5. In the Timeline Selector dropdown select 'Test (Cube)'
6. Open another application
7. Go back to Unity and observe the Timeline Selector menu

Expected result: 'Test (Cube)' is displayed in the Timeline Selector menu
Actual result: 'Test' is displayed in the Timeline Selector menu

Reproducible with: 2018.4.29f1 (Timeline is part of the Editor), Timeline 1.2.6, 1.5.1-pre.2 (2019.4.14f1, 2020.1.13f1, 2020.2.0b11, 2021.1.0b5)

Notes:
-The issue does not reproduce if instead of doing steps 4 and 5 you select the Cube object in the Hierarchy window