ss360Config.suggestions.maxSearchHistoryEntries = 0;
and you can limit the content groups to be searched via ss360Config.contentGroups.include = [ "My Content Group" ]
(both to be set in the Configuration Editor). I can send you the exact code you'd need to enter if you'd send me your Site ID (or a link to your site).
"suggestions": {
"maxSearchHistoryEntries": 0
}