I am trying to use Parse JSON to format contents of a variable. It will not let me click on the schema section and start typing. I tried making a test flow and that works; however, even when I copy the working Parse JSON action into this flow it removed the schema section and will not allow me to insert the test. I also made a copy of the flow that I want to run and then added a Parse JSON action there, but again, it removes the schema section. It will not even allow me to "Generate from Sample."
I had the exact same issue. Drove me nuts. For me, it was browser-related. I was using Internet Explorer, tried again on Edge, and it worked.
Hope this helps!
This just happened to a co-worker. The Schema box was disabled, or wouldn't let her type anything in it, when using Edge, but when she updated the same flow in Chrome, it allowed her to type it in. We even created a copy of the flow in Edge to see if it was just something with the original one, and it still wouldn't work in Edge. Worked without a problem in Chrome.