Custom Mail merge fields for word documents.

Hi,

I am currently working on a word document for mail merge. The way i am doing it is that i first create a word doc on my physical machine and i will then include fields which i will acquire from the drop down list. This drop down list can be found when you find an entity, click on it to see the summary and then click on tab called documents. In there start mail merge > create a template and there is the drop down list containing the fields available for merge documents.

Is there a way to add my custom fields to this drop down list without the need to change to view in SQL?

Thank you.