My main preference for QucsStudio is its similarity in user interface and "feel" to microwave circuit simulators such as Keysight ADS and Microwave Office AWR.   Also, like the commercial simulators, it offers a Harmonic Balance engine, in addition to the traditional Spice-like time-domain engine.

For me, a chief feature of Harmonic Balance is the ability to sweep a non-linear circuit for the steady-state response versus frequency, or input power, or some other input parameter.  Despite the available QucsStudio Example  project file for Harmonic Balance, for a long time, I was unable understand how to make these sweeps.

In the slides below for a diode detector, I show how it can be done.  It is not as intuitively obvious as I would have hoped, and perhaps this diode detector example will be useful as a reference.