So, I can partially reply to myself:

Sébastien Gendre <seb@k-7.ch> writes:
> # How to pass parameters to this function
>
> If I set a function as value to the variable `org-html-preamble`, this
> function will receive a plist containing all the export options.
>
> But can I set custom export option in the publish project alist ?
> And when I export manually a file, can I set custom export option on
> buffer level ?
>
> Or each option in the plist that my function receive need to be defined
> in the HTML export backend level ?

If I use org-publish, define a publish project and set a function as
its preamble: Any custom settings in the publish project will be put in the
info plist that the preamble function receive as parameter.

For example, if I define this function:

    (defun my/preamble-test (info)
      "docstring"
      (plist-get info :very-strawbery))


Then I set a publish project like this:

    (setq org-publish-project-alist
          '(("pages-org"
             :base-directory "./Pages/"
             :base-extension "org"
             :recursive t
             :publishing-function org-html-publish-to-html
             :publishing-directory "./public/"
             :html-doctype "html5"
             :html-html5-fancy t
             :very-strawbery "Test 1, test 2, test 3"
             :html-preamble my/preamble-test)))


And finally I publish the project "pages-org", in my published web pages
I get a preamble with the content "Test 1, test 2, test 3".


But if I set the variable `org-html-preamble` to my custom preamble
function like this:

(setq org-html-preamble 'my/preamble-test)

I cannot found a way to define "very-strawbery" value in an Org-mode
buffer and having it used while I manually export the Org-mode buffer.

I tried with "#+very-strawbery: test123" and "#+OPTIONS: very-strawbery:
test123", without success.

Someone have an idea ?



In conclusion, about this point: It is possible to define custom
Org-mode publish settings that will be available to a preamble function.
But, I cannot found a way to set the value of "very-strawbery" that is
used when I export an Org-mode buffer instead of publish it.


Best regards

-------
Gendre Sébastien