How to reproduce:
1. Open the "1253397_DisplayName" project
2. Open "123" Scene
3. Open the "CustomTrack.cs" script
4. Observe the classes and attributes in the script
5. Select "Cube" GameObject in the Hierarchy
6. Open the Timeline window
7. Right-click to add a Track (Notice that two Custom Tracks are present)
8. Add the "Custom Track"
9. Right-click on the "Custom Track" to add an Animation clip
10. Hover on the "Add SFX" menu item

Expected result: Tracks can be renamed and added into one category like clips
Actual result: Tracks can't be renamed and added into one category like clips (DisplayNameAttribute doesn't work)

Reproducible with: 2018.4.23f1, 2019.4.2f1 (1.2.14), 2020.1.0b12 (1.3.3), 2020.2.0a14 (1.4.0-preview.7)

Notes:
- DisplayNameAttribute works for clips and markers
- Added a reference on how to reproduce the issue in edit