You can hide the column by clicking on the column header dropdown and selecting hide. You do not have to remove the column since it’s part of a prefix and does not use any extra resources. You can remove the entire prefix via projection, but you cannot remove part of a prefix. This means that all columns that are under the prefix “test_file” will be removed.
To project a column, double click on the DATA column to bring up the Data Browser. Click on the drop down icon on the top right hand corner of of the menu bar. Select projection mode and select the columns that you would like to keep. Once done, click on the project icon.