bookmarker
/ˈbʊkˌmɑrkər/Definitions
1. noun
A person or thing that marks or indicates the location of a particular point in a book.
“The bookmarkers in the library helped patrons find their place in the long novel.”
2. verb
To mark or indicate the location of a particular point in a book.
“Can you bookmarker this page so I can find it later?”