Hi

Could exist a more general case than footnotes?

A kind of footnotes that work between different files?

Maybe the syntax could be [n:LABEL@ID]

Where the ID would be the unique ID of the heading.

Example:

** Reference
:PROPERTIES:
:ID:       978-84-362-7195-9
:END:

A “comment line” starts with a hash character (#) [n:102@978-84-362-7195-9] and either a whitespace character or the immediate end of the line.
...


** Notes

[n:102@978-84-362-7195-9] The hash character is important in orgmode.