To answer your questions.
1. The Extract Metadata step doesn't have a section associated with it. It also will not work for PDFs at this time. It primarily only support Bibliographic formats like documented at
https://wiki.lyrasis.org/pages/viewpage.action?pageId=104566672 . Uploading these same bibliographic files from the MyDSpace page will also trigger the metadata to be extracted in a brand new submission form.
2. DOI population already works if you perform a "lookup" from the MyDSpace page to start a new submission. On the MyDSpace page, at the top, next to the Drag & Drop section, there's an import button. If you click that, you can select to import from PubMed and other sources...and you can paste in a DOI there to find an article quickly, then click Import to start a new submission with its metadata.
Unfortunately, we've had to temporarily delay it at this time because of the complexity of this metadata comparison. I do expect it still will happen, but I don't have a timeline as we need to investigate it further.
Tim