When creating a new build step from an already created free style job with one step, adding this new step, fill it with data and then remove the previous step, makes the new introduced information become uneditable or in some cases moved from original location.

You can see an example in: https://youtu.be/hJqqDxfmJes

Although in this video you can see using groovy plugin, some different but incorrect behaviour also happens with other plugins.