I’m assuming most people will use the sends in the mixer more than the returns. Can anybody give me any tips how do use the returns.
They have a 1-to-1 relationship: whenever you create a send from track A to track B, a corresponding return is created in track B to represent the incoming connection from track A: https://blipinteractive.co.uk/nanostudio2/user-manual/Mixer.html#track-sendreturns
Yes, this way you can follow the chain from either end – a send channel will have returns for all the channels sending to it so it's easy to check.
But it's actually a good workflow hack opportunity because you can add many returns to a send channel (for example a reverb fx channel) all at once without jumping around channels to create sends. You can also mute (or delete) the returns individually. It's a really quick way to do things.
It’s the most flexible setup in all of iOS, imho. You can automate all those as well. It’s also how you do sidechaining when you want multiple sources as your trigger. You can send them all to one master side chain source.