! No, Einstein Search does not search the content of files. The search function within Quip, however, does search the content of files, so that kind of search can be performed there.

If the user is instead searching for the quip document using a search for the associated record, one way to get those kinds of links surfaced is to modify the search layout for that object to include that field. When the associated record appears in the UI, the user can hover over it, and the link will then appear in the record preview.