A commentary can be added without any reference. When you simply wish to extend on a note, place a cursor to that position and click Commentary and citation button from the toolbar.

Figure 4-16 Enter commentary without associating it with a reference.

A commentary/citation creates a little blue marker with ‡ symbol. You can update its content by selecting the symbol and clicking Commentary and citation button again. Also note that in the Commentary and citation dialog, a preview panel appears in the bottom. The preview feature is handy with references as you will see below.

A citation can be with or without your commentary. Let's look at a case with commentary first. 

Figure 4-17 Enter your commentary and associate it with a reference.

You can enter your commentary, and from the list of references, you can select one or more references. Use the search field to easily locate an appropriate reference. In the preview panel, you'll notice that your commentary appears before the list of references. 

If you want the references to appear in the middle of the commentary, use designated markers indicated with {#}. The number represents the ordering of the reference. If you have only one reference, indicate it with {1}. If there's more than one, subsequent references can be indicated with {2}, {3}, and so on.

As you can see the citation feature provides a flexible way to customize your commentary infused with references from the Reference Manager.