Thanks man... really, thank you very much for your time and effort you put into this thoughtful and quite specific answer!
I was now able to implement it in some sort. It's still not perfect, in the sense of still having simulation jerks when just placing particles back where they belong (or don't
), because of depenetration I guess (I may still do it mathematically incorrect and don't account for the scale change when placing particles back), but I think I do now understand better where the problems lie (definitely at my math side 
).
I get that 3D math is very important to understand to do stuff like this, so I'll try to learn and understand it better.
Thanks for your help along the way
All the best
Michael
I was now able to implement it in some sort. It's still not perfect, in the sense of still having simulation jerks when just placing particles back where they belong (or don't
), because of depenetration I guess (I may still do it mathematically incorrect and don't account for the scale change when placing particles back), but I think I do now understand better where the problems lie (definitely at my math side ). I get that 3D math is very important to understand to do stuff like this, so I'll try to learn and understand it better.
Thanks for your help along the way
All the best
Michael