Although it is not exactly "lightweight", I think the best thought-out (and best supported) workflow will consist of Pandoc and use its citation management, consisting of two (three) parts:
Which markup to put into your Markdown documents: this would look something like:
Important thing that needs lots of sources [@doe99; @smith2000; @smith2004].
or
@smith2004 state that thing is very important.
Possibly decorated with some location specifiers (e.g. pages or chapters within that source).
Your actual data that a citation wants to reference. Bib(La)TeX is the historical standard with lots of gotcha's concerning - not only - capitalization and names:
@Electronic{OSM,
Title = {{OpenStreetMap} database},
Author = {John Doe and Jane Smith and Johannes Diderik {van der Waals} and {{OpenStreetMap} contributors}},
Note = {Licensed under the Open Data Commons Open Database License (ODbL) by the OpenStreetMap Foundation (OSMF)},
Url = {https://www.openstreetmap.org/},
Year = {Accessed 2022--2025}
}
Manual maintenance is labor-intensive, but there is very good tool support. Random plug for JabRef which - like its competitors makes handling of such a database file bearable.
Newer and hotter is a JSON/YAML based metadata format, which is much more conducive to (semi-)manual maintenance.
references:
- id: Smith2004
author:
- family: Smith
given: Jon F.
- family: Doe
given: Jane
DOI: 12.3456/111222333-444
editor:
- family: van der Waals
given: Johannes Diderik
issued:
- year: 2019
language: en
page: 42-98
publisher: 'Santa Pub Inc.'
publisher-place: 'North Pole, Earth'
source: Crossref
title: >-
Super-long title that nicely shows how to wrap
such long strings in YAML
type: chapter
URL: 'https://example.com/the-book/chp11'
I cannot judge how good tool support is for that - it seems to be quite new.
This defines how citation syntax + bibliographic information is actually rendered in an output format (footnote + bibliography chapter, footnotes only, bibliography only, citation marker like [1], (2) or (Smith, 2021) and where and how any location specifiers (page numbers, cauthor-year]hapters) look like.
This of course also depends on the output format, be it Markdown, DOCX, PDF or HTML.