I experienced this same issue in Unity 2021.3.11f1, and confirmed the bug in multiple projects that were previously fine (only one of which was recently changed).
What MacOS version are you running? My best guess is that MacOS Ventura 13.1 broke some versions of Unity, as upgrading from macOS Monterey was the biggest change to my system this week (2019 MacBook Pro 16").
The following steps appear to have resolved the issue for me (so far so good):
- Reboot the computer (just to be sure)
- Backup the project (I just created an archived duplicate)
- Install Unity 2021.3.16f1 (the latest LTS release)
- Delete the project library (in case there's something weird cached)
- Open the project in the new version of Unity (which also regenerates the library)
I am now able to edit shader graphs again. Of note, deleting the library and regenerating in 2021.3.11f1 did not fix the issue. Only opening it and regenerating the library in 2021.3.16f1 worked for me.
I did not test leaving the old library intact while opening the project in the newest LTS version of Unity; it's possible regeneration isn't necessary, but it does seem like the safest bet. Especially if you didn't try removing the library before upgrading the project to Unity 20221.22f1 and you're still experiencing issues. You might try deleting the library to see if that resolves the issue now, without trying to downgrade to 2021.3.16f1?
There's a post over on the Unity Answers support site about this issue as well, but the login system appears to be broken (the irony!), so I can't respond there. https://answers.unity.com/questions/1927887/shader-graph-connections-not-visible.html