PGDLLIMPORT: patch or not to patch

Dear all!

(comment: my question relates only to the development area; so, please,
re-post to pgsql-hackers if it is allowed).

I use PostgreSQL under Windows quiet often and make my own builds in
msys2/mingw64 environment. Also I often experiments with the different
third-party extensions from the community. And as a result I often faces
with a PGDLLIMPORT macro to link all libraries and extensions with the
core postgres.exe.

For some extensions it is required to patch core and these extensions
insert missing PGDLLIMPORTs by itself. Other extensions are not ported
under Windows and I prepare my own patches (insert PGDLLIMPORTs) to
adopt its under my build environment and link shared libraries correctly.

My last case was the "extern ProcessingMode Mode;" variable in the
miscadmin.h which i patched by PGDLLIMPORT macro. I have discovered the
same modifications in some other extensions.

So, my questions are there any rules / descriptions / agreements inside
the PostgreSQL Project that define which global variables inside a core
code should by specified by a PGDLLIMPORT and which should not?? Or
there is freedom; you need this variable in the extension (under
Windows), make patch for it yourself! Or there is plan in the community
that all global non-static variables should be PGDLLIMPORT-ed by default
in the future?? What the right way to propose the PGDLLIMPORT patch to
the master and back-ported PostgreSQL code in order to avoid dup patches
in the extensions?

Thank you!

Regards,
George Tarasov