Sometimes you can't shoot during a beautiful golden hour, with fresh light pouring through the window onto your model. On those occasions, you have to fake it.
When shooting portraits you often don't have the control over the time you shoot, particularly if the images are not just for you. And sometimes, even if you do have control over the time, the weather decides you don't deserve the light you want and you're stuck anyway. As a photographer who lives in England and shoots primarily for other people and around the subjects' schedules, I am usually in both camps. As a result, I have to use lights to create various effects.
This video shows how to create the fake window light effect which looks so damned good. I haven't used it much myself for commercial work, but it's certainly a useful tool to have. As well as shooting light through windows, you can of course use a barn door modifier on the front of a strobe to similar ends. Furthermore, don't restrict your window light to just beautiful golden beams. With a blueish hue and a softer key light you can also add the appearance of moonlight or city lights outside. In a recent magazine shoot I fired a blue LED at a large window to give the illusion of nighttime despite it being around midday.
The best part about this technique? You can practice in lockdown!