There is no built-in way to upload multiple files to Plunker.
Users have built tools to facilitate this. Please see: https://www.npmjs.org/package/plunk which is a command-line utility that will let you create plunks from the contents of a directory.
You can also bootstrap plunks by making POST requests to http://plnkr.co/edit/ where the payload has the following format:
{
"description": "Plunk description", // Optional
"tags": ["tag1", "tag2", ..., "tagN"], // Optional
"files": {
"filename1.ext": "contents of filename1.ext",
"filename2.ext": "and so on.."
}
}
Code for this handler: https://github.com/filearts/plunker_www/blob/0c608ae80ef30d59bfdfeaf3c2a28563f7b730e4/app.coffee#L105-L121