@jack_cat
All of this discussion brings this old clip to mind ...
https://www.youtube.com/watch?v=TJ9f2rnjB84Regarding footnotes, since your bent is not programming, perhaps study citation management.
At the bottom of this page
https://www.citationmachine.net/chicagois this quote ..
How to Cite Sheet Music in Chicago Style
According to the Chicago Manual of Style, 17th edition, cite sheet music the same way as you cite books.
Once you’ve styled each and every reference, take a minute to run your paper through our plagiarism checker. It’s the perfect go-to resource when you’re in need of another set of eyes to scan your paper!
Now one of the best citation managers I have found is zotero used by professional librarians.
https://www.zotero.org/Two installations are required.
First, the application which runs in your desktop.
Second, an extension which is installed in your browser of choice.
Launch the "standalone" application. I installed mine here .. /opt/zotero/zotero
Open the GUI and you see “My Library” in left pane.
Now you can add “collections” of references (in your case music). You can arrange your library in different collections and sub-collections. You can even publish to the web.
When you browse to a particular site you open Zotero and highlight the collection into which you require to save your site. Then look at the extensions tool bar in your browser and you should see a Zotero icon which if you hover over it says .. “Save to Zotero ... ... ”
Now you have your reference (or references) you wish to cite and place in footnotes in your book you are writing via Scribus.
If you look in Zotero documentation there are various plugins.
https://www.zotero.org/support/word_processor_integrationIt also explains
Third-party plugins are also available for integrating Zotero with other word processors and writing systems.
https://www.zotero.org/support/plugins#word_processor_and_writing_integrationThere is ..
LaTeX, TeX, and Plain Text Editors
Now there is reference to Atom editor but you have given up on that idea.
and we read here ..
Zotero to InDesign export, by Kai• Basic implementation of a Zotero to Indesign export, allowing for LaTeX style citations of Zotero items in Adobe's InDesign
Now the thought occurs to me we should surely have a Zotero to Scribus plugin.
No matches for zotero in scribus site.
No matches for scribus in zotero site.
I would not expect you to write such a plugin but it is a subject for further thought.
Incidentally I am not on the Scribus development team. Music was not my best subject. I just experiment.