Not easily – unless you are using some footnote styles, where you can type the information outside the endnote field.
You might figure out a way to insert a “note” from the endnote “insert citation” tool, but you can’t combine it with a true endnote citation.
Finally, you might be able to use an unused field and insert that field in the Bibliography template for that reference type – so ref 1a might have a custom field that contained your text "for recent books see: " so it is included first. I really didn’t go thru all the steps to see if it would work.
I would usually relay this information in the in-text citation and not in the bibliograpy.
You cannot edit a word field and expect it to remain - unless it is the very last step before submission and you turn off CWYW or remove the endnote fields entirely from a copy of the manuscript (not the original or you won’t be able to go back during the response to reveiwers stage).
You delete the note, by deleting the number from the text of the paper and updating the bibliography (which should happen automatically when you next insert a citation).
what publisher?-- the footnote bibliography would require it fitting with the publisher’s style. There are multiple variations on footnote styles. Some have just the citation in the footnote itself and a full bibliography (Like Chicago 16 footnote) some put the bibliographic info into the footnote itself and if the citation repeats an earlier cited reference, the second footnote is shorter (short form).
For a footnote format, you first have to insert a footnote from your word processing software, then insert the citations into the footnote. It isn’t easy to have a document that is using regular insert citations and changing to a footnote style and visa versa. It requires some fancy macros that other users have provided elsewhere in the forums.
Footnote styles are common in humanities but rare in sciences. You might contact the journal or publisher to see how the editor would envision this information to be conveyed. Is it common in your field?