Once upon a time, long sync cables and expensive strobes were an absolute requirement for both studio and location-based photography requiring multiple controlled light sources. Later optical and wireless master/slave systems made the operation less clunky if still a tad expensive. But now there are even better and less costly methods.
Which allows me to plug one of my favorite pieces of gear: the Yongnuo YN-622C transceiver. Reminiscent of the similar and perhaps more famous Pocket Wizard, it not only allows the triggering of multiple speedlights wirelessly, but even allows for the changing of settings remotely through the camera’s menu system. For portrait work, I usually attach one of these, my speedlight, and an umbrella to a portable boom. But a bunch of these transceivers can also work together to accommodate multiple flashes in a sort of mini-network. Pure amazing!