...

• This transform might be automatically applied as one of the first steps of your recipe. See Initial Parsing Steps. 
• If you want to hide a column from view, select Hide from the column drop-down. Note that the data can still be referenced in your transforms and appears in any generated output. See Transformer Page. 
• If you are working with large datasets, you might want to delete columns at the beginning of your recipe, which can assist application and job execution performance. Use the tilde operator to specify ranges of columns.
• You can also specify the columns that you wish to retain and then add the Keep action to delete all other columns in the dataset.

...