EndNote references come with several custom fields that you can rename to represent aspects of the reference that might be important to your work. In the video below, the author uses an example of patient location for her medical research, which we will also demonstrate.
One of the advantages of creating a custom field is that you can add it to the display area in EndNote, which then allows you to sort the references in your library according to information from that field.
To create a custom field:
Go to Edit > Preferences. A pop up window will open.
Choose Reference Types from the left hand menu in the pop up window
Then hit the Modify Reference Types button on the right of the pop up window.
Choose a common reference type eg: journal article
Scroll down through the fields of journal article until you find a blank custom field
Then give that field a name (for example, "Patient Location")
Then click the Apply to All Ref Types button and hit OK
Finally, click Apply
When editing your references now you should see the new field
If you want to have this custom field as part of your EndNote display, right click over the headings above your EndNote references
Then select the custom field you edited from the drop down menu (it will still be called Custom Field, and not the name you gave it)
You can now sort by this field