Here's a solution to my question. Using the 'endnotes' package, we can define a function
% define a new citation function \newcommand{\mycite}[3][]{\let\theendnote\relax\endnotetext{``#2": \citet[#1]{#3}}} % arguments: 1: page (optional); 2: sentence fragment; 3: citation
Then it can be used as follows within the text:
\mycite[p. 32]{he wished to know the land}{heisenberg1949}
and then the citation will show up in the endnotes, without superscripted numbers, as
"he wished to know the land": Heisenberg (1949, p. 32)
For more complications, such as additional comments in the endnotes or multiple citations, we can define additional functions:
\newcommand{\myciteeg}[3][]{\let\theendnote\relax\endnotetext{``#2": E.g., \citet[#1]{#3}}} % the above, with an 'E.g.' \newcommand{\mycitesee}[3][]{\let\theendnote\relax\endnotetext{``#2": See \citet[#1]{#3}}} % the above, but with a 'See' \newcommand{\myendnote}[1]{\let\theendnote\relax\endnotetext{#1}} % for general endnotes \newcommand{\myciteinside}[3][]{{``#2": \citet[#1]{#3}}} % for multiple citations at one go; must use this as the first citation inside \myendnote \newcommand{\myciteinsideeg}[3][]{{``#2": E.g., \citet[#1]{#3}}} % the above, with an 'E.g.' \newcommand{\myciteinsidesee}[3][]{{``#2": See \citet[#1]{#3}}} % the above, but with a 'See'
and make citations like the following:
\myendnote{\myciteinside[pp. 258-259]{Darwin generally...goal}{gould2000}; see also \citet[pp. 242-243]{gould2003}}
which yields
"Darwin generally...goal": Gould (2000, pp. 258-259); see also Gould (2003, pp. 242-243)