There does not appear to be any way to insert "and" as part of an author name when adding to the library without this being interpreted as "&" for multiple authors.
For example, one can get free PDF files of government reports by "authors" whose names correctly contain the word "and" such as the "National Academies of Science, Engineering, and Medicine" in which case "Medicine" is not a separate author.
https://www.nap.edu/catalog/24625/th...-current-state
Even trying to change this manually by editing metadata does not work. It makes sense as an import default, but there should at least be a checkbox available when editing manually to disable this.