How to reproduce:
1. Open attached project "SGBugs.zip"
2. In Project window, open "New Shader Graph"
3. In Shader Graph, press Space to open Create Node panel
4. Hold Alt and click on any field that has nested children fields

Expected result: the fields recursively expand all
Actual result: alt does nothing, therefore, the field just expands regularly once

Reproducible with: 2020.1.0b9 (8.0.1), 2020.1.0f1 (8.2.0, 9.0.0-preview.14), 2020.2.0a18 (8.1.0, 9.0.0-preview.35)
Could not test with: 2018.4.25f1 (4.1.0), 2019.4.5f1 (7.3.1, 7.4.1) (the layout of the lists in the panel is different)