Using code blocks in Workflows has an extremely buggy UI, the lines disappear after several rows of code and with it the toggle functionality.
I collapsed some lines and now I can no longer open them because the fields disappeared.
Hello @Nicole_Reiter,
I apologize for this buggy behavior 
I tried to reproduce but was not able to get the line counters/numbers on the left side to disappear.
Let me know if you have any steps reproduce and I can see if there is a pattern that creates this bug. Are you self hosted or on the cloud? Self hosting older versions might be slightly more prone to UI bugs.