Q: What should I do if the status has remained 'Editor Invited' at Scientific Reports for three weeks?

You have three questions. Let’s take them one by one.

Where can you find the contact information for the journal editors?

Scientific Reports does not provide email IDs and other contact information for their editors, as you may know too. They provide a few group mails you could write to. So, you could have a look at the details on this page and write to the relevant mail ID. In your case, it will probably be the very first mail ID on the page.

How should you urge the editor?

Your article is presently at the ‘Editor Invited’ stage, which is quite a good thing. That is, it has been considered for peer review. However, finding the right profile and numbers of peer reviewers is always challenging, even for a Nature journal. So, you could wait for some more time to see if anything changes. Until then, you could drop them a mail at the ID mentioned on the page provided above to request for an update. Later, if you do need to ‘urge’ the editor (to process your manuscript within a certain time period), you could actually share the reasons (your academic dependency) for urging them to do so. For mail templates on communicating with journal editors, you may find this handbook useful (particularly Sections 6 and 7): A practical handbook of templates for communicating with the journal

Should you withdraw the manuscript?

Again, a month or so after submission is too soon to consider withdrawing the manuscript, especially as it has been considered for peer review, that too for a Nature journal. So, you could wait for some time. Until then, to be prepared for the next stage, you may go through the following resources that talk about various aspects of the peer review process:

• A complete overview of the peer review process [Course]
• Peer review process and editorial decision making at journals
• How to respond to comments by peer reviewers

Hope that helps. And all the best for the next steps!