Script type definition jenkinsfile environment variable

Write jenkinsfile form in the form of script, as follows:
def cusversion="Jenkinsfile"

Then the graphical editing pipeline, the environment variable will disappear after SAVE

No source file, test, or entry point is named. Start by reproducing the Jenkinsfile script-form environment-variable loss after saving the pipeline in the graphical editor, then trace the save path; done means the variable remains present after SAVE.

Written by the indexing model from the issue text.