The Diff Tool

The Diff Tool is used to compare workflows, runs, and text files (like namelists).

Click on the "Workflow" radio button on the left, then select your workflows in the drop down boxes. In this example we're comparing "wrf-EastCoast" and "wrf-EastCoast2". All names, dates, tasks, environment variables, and namelists are compared, with differences highlighted in red. In this screen image below, we see that the NAME and MODIFIED_DATE fields are different. Just drag the scroll bar down to continue the comparison.

Further down, we see that the start_date and end_date fields in namelist.wps are different.

You can also use the Diff Tool to diff two files on disk. Just click on the "Text files from disk" radio button on the upper left, then click on the "Load Text File" buttons to select your two files.

After pressing the "Diff" button, I see the differences between namelist.input and namelist.input2 (loaded from my local Windows disk).
Note: the hint message is telling you that you may need to add blank lines to one or the other file in order to line up like sections (so the tool can compare them).