@irene– Welcome to the Piklist community!
When you press “Add New Post”, WordPress sets the Post Status to auto-draft. So just use the status parameter to tell Piklist you only want to show the meta box when the post status is auto-draft.
Add this to your comment block:
Status: auto-draft
No need to use the new attribute. new is really used to NOT show a metabox on the new page: New: false.
Let us know if you need anything else.