In Scrivener 1, the word list file is stored in %LOCALAPPDATA%\Scrivener\Scrivener\wordlists.ini. If you haven’t already added any words to the custom list in Scrivener 3, you can copy that older file and use it to replace the file in the new location used by Scrivener 3.1.4.1, %LOCALAPPDATA%\LiteratureAndLatte\Scrivener\wordlists.ini. Alternatively, you can open the older file in a plain-text editor (Notepad will do fine) and copy the words in the Personal= line, then open the new Scrivener 3 file, add a comma and space following the last word listed there, then paste in the words copied from the Scrivener 1 file.
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