Literary term for visual consistency or uniformity of paragraphs?

The terminology describing paragraph and page lengths, and the awkwardness of the last word of a paragraph on a line alone (or worse, at the top of a new page) is part of book design. Wikipedia has an good article about it. https://en.m.wikipedia.org/wiki/Book_design

Copy editors aren’t the people who deal with this, because when they’re editing they don’t yet know how the text will look on the page. Once the book is set in type and the book design established, proofreaders will identify the problems and may adjust the text or its spacing to maintain a pleasing appearance. Isolated lines or words have catchy names—-widows and orphans.

A book like the Chicago Manual of Style covers some of the basic principles.