Suggestions for postnotes
The following packages have something in common with the package postnotes. The packages are ordered in decreasing similarity.
- enotez: Support for end-notes
 - endnotes: Place footnotes at the end
 - fn2end: Convert footnotes to endnotes
 - pagenote: Notes at end of document
 - endnotes-hy: Patches the endnotes package to create hypertext links to the correct anchors
 - endheads: Running headers of the form “Notes to pp.xx-yy”
 - endnote: Generic “endnotes” code
 - endiagram: Easy creation of potential energy curve diagrams
 - substances: A database of chemicals
 - chemformula: Command for typesetting chemical formulas and reactions
 - erw-l3: Utilities based on LaTeX3
 - secnum: A macro to format section numbering intuitively
 - clistmap: Map and iterate over LaTeX3 clists
 - ninecolors: Select colors with proper WCAG color contrast
 - xsim: eXercise Sheets IMproved
 - handoutwithnotes: Create Handouts with notes from your LaTeX beamer presentation
 - fnpct: Manage footnote marks’ interaction with punctuation
 - grading-scheme: Typeset grading schemes in tabular format
 - chemmacros: A collection of macros to support typesetting chemistry documents
 - acro: Typeset acronyms
 - chinesechess: Typeset Chinese chess with l3draw
 - cprotectinside: Use cprotect arbitrarily nested
 - rescansync: Re-scan tokens with synctex information
 - precattl: Prepare special catcodes from token list
 - wrapstuff: Wrapping text around stuff
 - pdfoverlay: A LaTeX style for overlaying text on a PDF
 - darkmode: General Dark Mode Support for LaTeX-Documents
 - abspos: Absolute placement with coffins
 - media4svg: Multimedia inclusion for the dvisvgm backend
 - cvss: Compute and display CVSS base scores
 - saveenv: Save environment content verbatim