The Order tab on the query canvas represents the Order By section (SQL clause) of your query.
This allows you to set the order in which your table of data will be returned. You can have zero or more items in the Order tab.
You can set ascending or decensing by left clicking on the top right of the nameplate of the order tile
You can add columns to the Order tab by either double-clicking or dragging them on.
If you are using a scalar function (such as length or max) in your Select tab, you must give them an alias. They will then appear under the S menu on the query canvas quick bar to the left hand side (shown above).