In my template I'd like to capture the entry_id of my main channel:entries loop, because I have subsequent loops where I may want to avoid that entry in one case, and invoke it again in another. So I'm looking for some way to create a variable that will allow me to do this. But the only user-defined variables I've found so far are the preload_replace ones, which happen before the channel:entries are run, so no good for my purposes.
Are there other user-defined variables I may have missed? How would you do this?