@Eden Penfield - this is an interesting one! I wonder whether some of the workflow starts in Salesforce here and you would need to use a roll up summary field i.e. you could rollup the number of Opportunities that were closed won (once closed won Opp is marked then it’s effectively not a new logo) therefore any Account with rollup of closed won Opps = 0 is technically a new logo. This would be on the Account record obviously and could then be used in Account Engagement module in Clari or you could use SFDC workflow or trigger to mark the ‘new logo’ on associated Opportunities and then that could subsequently be used in Clari. 

Possibly a slightly convoluted way to get what you need but I think something like this would technically work (although a more decorated Salesforce admin than me would be able to confirm!).