STR:
1. Create a new project
2. Add a shader from the Example section to the project: https://docs.unity3d.com/Manual/SL-GrabPass.html
3. Create a new shader variant collection asset
4. Add the shader from step 2 to the variant collection
5. Click on the + sign right above the "Add shader" button, a new window opens
6. Select Normal<No Keywords> in the window from step 5.
7. Click "Add 1 selected variants"

Expected: variant is added
Actual: an error is thrown: ArgumentException: shader GrabPassInvert pass type 0 does not have a shader snippet

Reproduced on 2020.2.0a19.
I saw a report on the forum from 2016, so it's not a regression :)
(https://forum.unity.com/threads/problem-adding-shader-variants-with-grabpass.440267/)