The underlying feature arrived a while ago, but we've just made it discoverable:
(Notice that the last one has no right arrowhead; three is the limit.) The function input to MAP is given three inputs: the individual item, that item's position in the list, and the entire list. It may not be obvious from the pictures, but all I did between stages was to click the right arrowhead; these names are automatically provided.
So, you want every other item of a list?
You want a (toplevel) copy of a list?
This illustrates a subtle change: Normally, if you drag a variable into a Reporter input slot, the ring disappears, because 99% of the time, what you mean is that the variable's value is the function you want to use, not that you want to use the niladic function that returns the variable's value. The new thing is that if the variable you drag in is one of the ring's own formal parameters, then the ring doesn't disappear. So this says to call the identity function on each item of the list.
But that particular use case is common enough that we interpret an empty ring as the identity function:
This seemed like the right thing because leaving an input slot empty means to substitute the input into that slot, and you can think of the empty ring as one big empty slot, so it's fairly mnemonic, And the previous behavior (reporting an empty ring) was entirely useless.
Note that the value/index/list thing does not apply in COMBINE, which requires a two-input function. Nor does it apply in rings that aren't in HOFs.