You can insert a line into the dataconst table of that project in the db (see this example provided by Micro Focus):

insert into dataconst values ('AUTO_MAIL_SUBJECT_FORMAT',
'DEFAULT.TESTPROJ - Defect # ?BG_BUG_ID has been created or updated -
?BG_SUMMARY')

If you want to add a field you put a question mark in front of the field id as above for ''BG_BUG_ID'' or ''BG_SUMMARY'' or for example if you had a UDF such as ''BG_USER_01''