According to the documentation <$action-sendmessage $message="tm-new-tiddler" ...> only knows about three possible parameters names:
param
The optional title of a tiddler to use as a template for the new tiddler
paramObject
Optional hashmap of additional tiddler fields
navigateFromTitle
Title of the tiddler from which the navigation to the new tiddler was initiated
However, you used title="$pfix$".. and "title" is not a recognized param name for this message.
You need to use $param="$pfix$" instead. If you make that one change, then the "auto numbering" will work as you expected.
enjoy,
-e
Eric Shulman
ELS Design Studios
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