How to force line number annotations on inner margin in reledmac?

The line number annotation are annotations to the line number. So, setting the line number position will set the line number annotations. You can do it using \linenummargin (§ 5.3.4 of the handbook), you can also set the side note margin usinge \sidenotemargin (§ 12.1).

So

\documentclass[twoside,10pt]{book} \usepackage[paperheight=9in,paperwidth=6in,inner=1.in,outer=1.25in,top=0.6in,bottom=0.6in,heightrounded,marginpar=1.5cm]{geometry} \usepackage[noresetlinenumannotation, series={A}, noend,noeledsec,nofamiliar,noledgroup]{reledmac} \newcommand{\bv}[1]{\linenumannotation{#1}} \makeatletter \Xwraplinenumannotation{\@firstofone} \renewcommand{\linenumrep}[1]{} \makeatother \Xnoidenticallinenumannotation \linenummargin{inner} \sidenotemargin{outer} \begin{document} sss \newpage \begin{center} \textbf{\large Chapter I}\par \textit{\scriptsize The pedegree of Jesus, to shew that he is Christ, promised to * Abraham and * David. 18. That he was conceived and borne of a Virgin, as Esay prophesied of him.}\par \end{center} \firstlinenum{1} \linenumincrement{1} \beginnumbering \pstart The \bv{1} booke of the * \ledsidenote{\scriptsize \flushleft This Goſpel is moſt ſolemly ſung in holy Church at Matins upon Chriſtmas day.} generation of {\scshape Jesus} Christ, the ſonne of David, the ſonne of Abraham.\par †\bv{2}* \ledsidenote{\scriptsize \flushleft As alſo it is the Goſpel of the \textbf{\emph{Conception}} and \textbf{\emph{Nativitie}} of our Blessed Lady: becauſe here is declared the pedegree of her alſo.} Abraham begat Iſaac, And Iſaac begat Jacob. And Jacob begat Judas and his brethren/par \pend \endnumbering \end{document}