If I only have one {L} Energy in my discard pile, can I use Tapu Koko {*}'s "Dance of the Ancients" Ability to put it on one of my Benched Pokemon?
Yes, you would do as much as you can.
Source: Team Up FAQ (2019-01-18), TPCi Rules Team (2019-01-31)

Relevant cards

Note: All applicable cards may not be listed below.
SM9_51
SM9_51