If you have coded in any language, you must know about dictionaries. They can convert text. For example, in a dictionary with a key “Mar” and a value “March”, it will report “March” if you typed in “Mar.” I’ve accomplished this with a custom block. The project can be found here. Some visual examples can be found below.
Nice idea to build a set of dictionary blocks 
I'm wondering if it might be better to accept a list of pairs rather than two lists - just to keep the key and the values together so they don't get out of sync
Thanks! I might consider this. I’ll make another block in the project for that.
EDIT: I made the block with 2 list parameters, so new users on Snap would understand it a bit better