Short answer: Don’t contact editors about submitted work unless you forgot to include entire pages of a piece of fiction or a full poetry manuscript.
The only time you should contact an editor after sending a submission is to let them know that the work has been accepted for publication elsewhere. In this instance, it’s polite to notify the editor as soon as you’ve heard about the other acceptance, and to thank them for their time and consideration. You might let them know where the work is scheduled for publication if you wish.
You can also withdraw a piece from consideration. This option should be used very sparingly and only when absolutely necessary. Editors don’t like to start processing and considering a submission and then be told that a writer has decided to rescind the work. It’s a waste of resources and can jeopardize your chances of receiving serious consideration at that press again in the future.
Do consider withdrawing your submission and re-submitting if you realize you left off the last page of your short story, for example, as this saves administration extra steps with regards to adding in the missing page. In this case, include a brief note with your withdrawal and a new cover letter explaining why you’re resubmitting. I would not recommend doing this for poetry, though eg. if you meant to send 5 pieces and only sent 4.
If you decide to change a character’s name in a short story or revise one stanza in a poem, definitely don’t contact an editor to let them know. If an editor chooses to accept your piece, they will likely give you the opportunity to make minor changes before publication. Again, this comes down to respecting a publisher’s resources; in most cases, they simply don’t have the means to track all your revisions before making a final decision. It’s also safe to say that if they do / don’t like your work, one line change is not going to significantly sway their opinion one way or the other.
— Nicole Melanson