We need a way to hand-off more than one result (or channel). For instance you might have one filter that gets the name of a product, and another that gets the name of the company that makes the product. Today we can’t distinguish the two because the output is just the title of a tiddler or <currentTiddler>. What if had a an operator like "store<OUTPUT variable name>"
e.g.
[[filter that finds product]store[product]] [[filter that finds company]store[company]] +[[ is made by ]addprefix<product>addsuffix<company>]]
By doing it this way, you don’t need two nested list filters – everything can be done in one filter run expression.