I’m not sure how this function named correctly, but AFAIK it present in Reaper and Studio One.
The sense is, that you can make kinda send for insert plugin.
For example - you put reverb on insert and want process it with filter and compressor. But reverb only, without touching source signal.
Or, you want use filter on insert saturator, but only on saturator signal, keeping source signal untouched.
So, it’s kinda send from insert or individual send, I suppose.
You can say, that I can make it with common send. Well, yes. But if you have to make multitrack while finish project, you’d better avoid sends - to
have opportunity use Export Multiple Channels. Besides, if you use send to some saturator plugins, they can increase gain enough, despite on pre/post settings, so you have additionally correct gains in this case.
Also to make this idea complete - “HOST Mix button” on inserts would be nice! Yep, nowadays most of plugins have it, but still some not. So it would be great to have it anyway.
Hope it make sense.)))