When working with many values in the AttributeValueMapper, like the case when you have imported from a lookup table, it would be very useful to sort both the columns Input Value and Output Value both numerical and alphabetical. Just like the Table view in Data Inspector works.
(there were an old similar idea which got sort of an answer but manual sorting is not what I need when I have many values in the AttributeValueMapper transformer: https://community.safe.com/s/bridea/a0r4Q00000HbrJdQAJ/sorting-attributes-attributevaluemapper )