I am trying ot figure out if I can create a simplified syntax for a
particular special block in a derived HTML exporter.

I'm trying to produce HTML like this:

<div class="r-stack>  <img data-fragment="fade-out" src="...."/>  <img
data-fragment="fade-in" src="..."/></div>

The derived backend (org-re-reveal) already has an

#+ATTR_REVEAL that an make the data-fragment attributes, so it's not
hard to produce
 the desired outpu:

#+begin_r-stack
#+ATTR_REVEAL: :frag appear[[imglink1]]
#+ATTR_REVEAL: :frag appear[[imglink2]]#+end_r-stack

However, I'd really like to add a less verbose syntax, like this:

#+begin_r-stack :frag (appear appear)[[imglink1]][[imglink2]]#+end_r-stack

My question is: will the exporter preserve information from these
header-like arguments, and is
there a mechanism I can use in a custom ~special-block-function~ to
make use of htem?

Thanks for your help as always!

Matt