Reproduction steps:
1. Open the attached “IN-94692.zip” project
2. Select “ProbuilderStandardVertexColor.shadergraph” from the Project Window
3. In the Inspector, press the dropdown button right side of ‘Compile and show code’
4. Observe the loading bar and the opened pop-up

Expected result: The pop-up opens immediately and the number of variants is around 400
Actual result: The pop-up takes more than 1 minute to open and the number of variants is more than 2 million

Reproducible with: 6000.0.25f1, 6000.0.38f1, 6000.1.0b6, 6000.2.0a3
Not reproducible with: 2022.3.58f1, 6000.0.24f1

Reproduced on: Windows 11, macOS (M4 Max)
Not reproduced on: No other environment tested

Notes:
- In 6000.1 and 6000.2 versions the number of variants goes up to 9 million
- Also reproduces on a new project with URP or HDRP Lit Shader Graph. It does not reproduce with Built-In Lit Shader Graph
- Does not reproduce with Unlit Shader Graph