This error occurs when trying to use declarative pipeline for a file parameter.
"This pipeline uses input types that are unsupported. Use Jenkins Classic to resolve parametrized build."
Could support for file be added?
choice(name: 'Environment', choices: 'DEV\nQA\nSTAGE\nPROD', description: 'Which environment to import to.')
file(name: 'import.json', description: 'The file to import.')