Can one take a Siddur off the shelf five minutes before Shabbos is over for Ma’ariv, or is it מכין משבת לחול?
No, unless you use it a little on Shabbos. See also here: https://asktherav.com/13436-earliest-maariv-when-motzei-shabbos-is-yom-tov/ שמירת שבת כהלכתה פרק כ''ח סע''ד והערה קע''ג. #11007
