FOUND A SOLUTION
My new event was only using outputs.
Step 1: Add any input node. I used boolean as it is the default choice.
Step 2: (not sure you NEED to do this but will put it just in case) Hook up the input to anything. I used a branch but did NOT hook any of its exec pins
Step 3: Restart editor and see that your changes saved this time!
Step 4: Remove the random input variable you added earlier.
Step 5: Restart editor again and it saves properly!