You can edit a query component in the "Format Query" dialog. This has pages for Columns, Sort Orders and Filters, as well as Queries (see Editing a query).
There are various ways of opening the dialog:
In Database Manager right-click on the query component name (this will be under the relevant table or relation name either in Column Views, Sort Orders, or Filters) and select Format.
If you are already in a table, query table or relation, you can select Query, Sort Order, Columns or Filter from the Format menu. Alternatively click on the relevant button on the Query toolbar.
You can edit the query component by selecting the component name in the Name box and making changes as required in the body of the dialog. When you click on OK or move to another page in "Format Query", you will be asked if you want to save the edited component. Click on Yes and the component will be saved with the changes made.
If you also change the name of the component, you will be asked if you want to create a new component. In this case the edited component will be saved under its new name and the original component will not be changed.
If you want to delete the original you can do this in Database Manager (see Deleting a database object).