concatenate tasks


I don't know of a way to do that, but there is a suggested idea that you can vote on that would allow for dependent tasks. I believe that might get you closer to what you're looking for. Unfortunately it hasn't yet been implemented by the developers (though I'm sure they're working hard on it).
You can go here to read about it and vote on it:
https://www.rememberthemilk.com/forums/ideas/1691/
You can go here to read about it and vote on it:
https://www.rememberthemilk.com/forums/ideas/1691/