Well...
Cakewalk has it (had for many years), FL Studio has it's own settings, click "gear" on VST tab and you will some pretty cool controls...including Solo and others, such as scaling/DPI awareness.
Solo / Mute is a convenience item, not something completely new. I find it very useful when working with VST/VSTi that requires fast A/B audition between with & without main arrangement. When programming or changing values, so you don't poke mixer and then go back to VST UI, especially on dual screen setup.