I'm about to submit my first scholarly manuscript to the top journal in my field, which has an acceptance rate of 20-25%. One of the co-authors on my paper, besides being generally well-known in this field, happens to be on the editorial board of this journal as an associate editor. Obviously I imagine that he'll automatically be excluded from the review process due to conflict of interest, but does their affiliation with the journal increase the chance of the paper getting accepted? I should note that the paper has already been through several rounds of internal revision and I've received excellent feedback so far from both this particular coauthor and others.
All things considered, a paper coauthored by an editor should not improve the chances of getting accepted.
It is unlikely that the reviewers will be aware that one of the coauthors is an associate editor, so their reviews will be probably not be influenced by that. This is even more obvious in case the reviews are double-blind.
It is possible (although also unlikely) that the editor responsible for your paper might take a slightly more favorable view to your paper in case the reviews are borderline. However, in any case this will not improve your chances much.