I contacted their technical help and got this response.
Thank you for contacting Thomson Reuters Technical Support. We are happy to assist you.
EndNote’s Term Lists are used for the abbreviation and the Journal Terms list is only used for Journal Name abbreviation substitution. This does not extend to any other field, including the Series.
The only 3 fields that can use any substitution/terms list are the Journal, Author and Notes fields, and the Notes field does not allow for substitution.
I apologize for any inconvenience this may have caused you.
I would be glad to forward your comments to our development team for consideration for future releases of EndNote.
I would also suggest that you and any other user who wants to see this feature, submit a request via our suggestion form. The more requests for a feature, the more likely you are to see it:
This is the best way to make your voice heard when it comes to anything you may want to see included in the software. While messages sent through this form are rarely returned, each one is read by our development staff for consideration for future program updates.
We appreciate your comments and your willingness to help make our products better for all users.
As a work-around, I would suggest waiting until you are completely done working on your paper. Then, use the Tools > EndNote X2 > Remove Field Codes command in Word. You will be prompted to save a new copy of the document. Save this and also your original somewhere safe, and then edit your references manually as needed.
**PLEASE NOTE** Removal of the field codes will permanently break the “link” between EndNote and the current copy of the paper. If after removing field codes you need to further edit your references using your EndNote program, you will need to return to your original copy of your paper with the field codes intact.
I hope this information helps! Please let me know if you have any additional questions regarding this issue.
Based on the information provided above, this case will be closed and no further action is required on your part. However, if this does not resolve your issue, please reply to this email and your case will be immediately reopened for additional support.
Product Support Analyst