Getting section number via Action code

Export code includes a code ^sectionNumber^ which gives output like this 1.18.29. It is effectively a chaining off all the $SiblingOrder values for ancestors and that of the current note.

This can be achieved in action code but is somewhat inelegant as root level notes require a different handling and action code conditionals require a full expression inside the branch. This to set $MyString to the section number use:

$MyString = if($OutlineDepth >1){
   collect(ancestor,$SiblingOrder).reverse.format(".")+"."+$SiblingOrder;
}else{
   $SiblingOrder
};

Or, in one-line form: