expand a rule #grammar

gistfile1.txt

In S05, is there a way to "expand" a rule within another?
Example, <=v> whould expand the productions of v within a
rule so that

  token t { <=v> | <d> }
  token v  { <a> | <b> | <c>  }

Compared to C<< <=v> >>,  C<< <=v> would
would avoid an additional level in the parse tree, that would
be equivalent to :

  token t   { <a> | [ <b> | <c> | <d> ] }

that is to :

  token t   { <a> | [ <b> | <c> | <d> ] }