Steps To Reproduce:
1. Create a new Project
2. Window > Package Manager>Shader Graph> Import
3. Project > Shader > Create Blank shader graph
4. Double click on the shader to open it in the editor
5. Shader Graph > Blackboard > Add properties/Resize to see the Scrollbar
6. Scroll using the scrollbar

Expected result: The Blackboard window scrolls up/down

Actual result: The Blackboard window does not scroll

Reproducible In: 2021.2.0a7, 2021.1.0b9

Not reproducible In: 2020.2.2f1 (package: 10.2.2)

Reproducible with Package version: 11.0.0, 12.0.0

The same bug has been reported earlier: https://fogbugz.unity3d.com/f/cases/1291760/ for 2020.2

Environment: Win and Mac