Free diagram softwares like
draw.io are capable to glue links to every diagram element you like. These links will be exported to SVG.
My idea is to use these SVG links from Sphinx (Myst) to link to the document content.
IMHO there are many applications for this:
Diagram parts linking to other documents
Diagram parts linking to other diagrams
This is not so easy to implement into sphinx - some core components have to be changed.
So please have a look at
for updates on this matter.
I would be happy go get feedback from the community on my proposal.
Cheers,
Volker