The User Dictionary is a Text file in the normally
hidden Application Data folder
XP xample:
Code:
C:\Documents and Settings\<user logon>\Local Settings\Application Data\sigil-ebook\sigil\user_dictionaries
It seems you can just use a text editor (notepad++) that maintains the EOL (LF only) (if your list uses CRLF, open that in NP++ and convert the EOL)
and add the list in Alpha order
OR just add the file to the folder (with proper EOL)