To save with different rules you’ve got to change the contents in the Naming Script option setup as there is no way to use a different script when saving from either Left or Right without code changes/additions to support / store multiple Naming Scripts similar to how the Tagger Scripts can be chosen from the Contextual Menu now?
Except that Naming Scripts would default to the first one. If you want to use any other rules to save against, you’ll need to use the Contextual Menu to select a Naming Script the same way a Tagger Script is selected.
Though I suppose if you want that functionality now it could be set using some hardly used tag to hold a value.
Before saving, select all your stuff that you want saved differently and add/edit some hardly used tag:
$if($eq_any(%bpm%,666,777,888,),
$set(%_saveScriptRules%,%bpm%),$set(%_saveScriptRules%,999)
$if($in(%_saveScriptRules%,666), ... build %_pathNameForSave% ... )
$if($in(%_saveScriptRules%,777), ... build %_pathNameForSave% ... )
$if($in(%_saveScriptRules%,888), ... build %_pathNameForSave% ... )
$if($in(%_saveScriptRules%,999), ... build %_pathNameForSave% ... )
$noop(and then finish up the rest/common stuff next)
$set(_fileNameForSave, %artist% - %title% %_fee%%_fi%%_fo%%_fum% Do As I say Here)
$noop( ...and finish by)
%_pathNameForSave%/%_fileNameForSave%