Originally Posted by rozen
I would appreciate any suggestion as to what I am doing wrong.
Builtins are stored online and are automatically fetched then used for the recipe. Custom recipes are stored in the database. I must admit, I'm not sure what the local copy of the builtin is used for (but I'm very glad it's there - I search there often). As Kovid said, you need to create a custom recipe to have Calibre use it.