The only way I can see this working (if you say that PT does that), is that PT infact inserts x-number of extra plugins as "Ghost plugins". So you think you insterted one for all channels, but in fact there are multiple who are controlled by the GUI of the one that is visible. And that is the exact discription of a VST3 plugin.
That's exactly what protools does.
And by default, all mono instances are controlled by the one visible.
Except you can view any of the instances, and you can choose to link any combination of instances.
Which leads to adjusting differently the different instances in the same insert slots.
But really, I do not see the point, not at all.
I actually find the VST3 plugins (which are doing the exact thing you are asking for) not very usefull.
I rarely find myself into a situation where I want all my channels being processed in the same way.
As an example, let's take the most common channel format, 5.1.
I'm not going into differences between front, back and center, but the LFE channel alone should explain this very well. There is no thinkable situation, configuration or user case where we would want to process the LFE the same way any of the other channels is processed. I am very happy that I can insert a mono plugin into my LFE channel for applying Low Pass filtering, limiting, generating sub harmonics and everything else that comes with the use of an LFE channel.
Exactly the point Fredo !
That is because in many surround situations you'd want to adjust differently various sets of channels, that this function is really useful.
The LFe example is not a very good one imho, because it concerns one channel that is is truly separated and really different from all others. So yes, for the Lfe channel, you'd want to use Lfe only targeted insert.
It's not the same story when you want to, say, eq front and rear with the same plug, but with different parameters.
In Nuendo you have to use two plugins slots for that... One for front, on for rear.
In Protools, it is true that you can use one multi-mono plug in one insert slot and having Two control groups : one for front, the other for rear.
In regards of automation, it doesn't change anything, because on the one hand (PT) you have to deal with one slot, but multiple invisible groups of parameters (buggy if you're not extremely cautious), and on the other hand (N) you have to insert 2 plugs (using just the same amount of instances by the way) 1 insert for front, 1 insert for rear.
Automation is then more secure, but you use 2 slots out of 6 (The 2 post fader don't count because PT don't has that)
That's why in the end I got used (pretty quickly) to Nuendo and that's why I wouldn't want to see the whole "multi-mono" old paradigm from PT on Nuendo.
So, not the whole paradigm, but maybe having the ability to in fact insert a VST3 on one slot, say 5.1, and be able if you want to differently control front/rear/lfe, yes, but in the same insert slot !
Winner on both sides.
One use for that is that you can save presets for your plug with different parameters on different sets of channels, same slot.
I'm not sure this is crystal clear, but knowing the actual difference between the two daws, I see here a good opportunity for Nuendo to address all combinations if that could be implemented.