What Kiwi.com Nomad does, for reference
Kiwi.com’s own description: Nomad “allows you to input multiple destinations and your desired duration of stay in each of them, before it calculates the cheapest possible route,” and it “shuffles the destinations you input and finds you the most cost-effective itinerary.” You set a departure city and date, the nights away, the places and the nights in each; three or more destinations. You book on Kiwi.com, and the page describes the Kiwi.com Guarantee for a connection missed because of a delay. It is the right tool when you want the route and the booking in one place.
What people look for an alternative for: a window of dates rather than one departure date, trains where they beat the plane, seeing the orders that came close and what each would cost, and booking with the airline rather than through an agency.