Glue - Change Schema - Dropdown for target key or custom visual transform

In our ETL process we are building out a pipeline where someones job is to take input files (ex. csv) and map the columns to existing column names. After the mapping is complete a glue workflow will perform all of the needed data post processing and eventually loading the data into our database. We will be ingesting 3k+ data sources.

The "Change Schema" widget almost works as intended. The only hangup is that the "Target key" value is a manual input. Ideally this would be a populated list containing column names from our database but can alternatively be a static list that we update as the schema changes.

So there's two questions:

1. Is it possible to specify a dropdown list for "Target key" using the Change Schema visual transform?
2. If not, is it possible to create a multi column custom visual transform? All I need in the transform is two columns side by side. One for "Source key" and one for "Target key" where target key is a dropdown list. The issue I am running into here is that I can't seem to create a multi-column json template. We don't even need to select the data type at this stage.