This is a disclaimer to my former message about this subject.
I continued considering the solution to the problem of using *fleurons* in a document via the suggested *\leaders* command and it turned out to be a dead end for the following reasons:
1) it acts wrongly if the page in which the *fleuron* is to appear has a lot of blank space availabe, as the following test code demonstrates:
\setuplayout[lines=30]
\def\Fleuron
{\par
\leaders\vbox to \lineheight{\midaligned{Finis\\coronat\\opus}}\vfil} \starttext
\dorecurse{32}{Line \recurselevel\par}
\Fleuron
\stoptext
where the intended *fleuron* appears superposed several times instead of the only one desired;
2) the use of such an instruction is touchy and not dependable. As I have experienced, things work satisfactorily or not according to the degree of nesting of the command *\fleuron* in the whole launching command and possibly according to many other unnoticed factors;
3) the suggested formulation does not allow enough control for the placement of the *fleuron* in the final document.
In the end all this seems reasonable: the straigth use of the *\leaders* command is almost the contrary of the one demanded for the present functionality. The effect of the (obscure in more than one sense) *Tex* command *\leaders* is to fill a (rather implicitly defined) surface with repeated copies of a certain motive. The visibility or not of the result according to the surrounding text or space in the page has to be considered therefore as a purely accidental (and noxious) side effect. The content typesett via *\leaders* is not supposed in any way to disappear when following lines are added.
I conclude that the only lawful use of *\leaders* in the true context of *fleurons* would be for the generation of certain repetitive motives (for instance a kind of small checkered board), but this is only a hint; I have not explored this possibility.
Fortunately I have been able to advance in another direction and to get what seems to me a consistent solution to the original problem. I open the new thread *Using *fleurons** for explaining it more fully.
Regards
Francisco