Per suggestion of "User:The Evil IP address" at translatewiki
'watchlistedit-raw-legend' => 'Edit raw watchlist',
'watchlistedit-raw-explain' => 'Titles on your watchlist are shown below, and can be edited by adding to and removing from the list;
one title per line.
-When finished, click Update Watchlist.
+When finished, click "{{int:Watchlistedit-raw-submit}}".
You can also [[Special:Watchlist/edit|use the standard editor]].',
'watchlistedit-raw-titles' => 'Titles:',
'watchlistedit-raw-submit' => 'Update watchlist',