The Data Manager has no direct way to either add mapping tables or use applymap function.
It would be nice if a two-field table could be flagged in the load wizard as being a mapping table. And even nicer if there was an additional "Lookup" transformation card to provide the Applymap functionality, i.e. name the map table and the key field, and add the returned value (3rd parameter optional) as a new field in the table edit grid.
I would expect that the script generator for this would be much simpler than the other cards such as replace, bucket etc. as the Applymap function only has 3 parameters. Even without nesting this would be a great addition ?