If I have multiple Poliwag on my bench, does Politoed's "Lordly Songleader" attack do additional damage for each of those Pokemon?
You only get the additional bonus once per Pokemon named in the attack. For example, if you have two or more Poliwag on the bench you only get to add +60 once.
Source: Lost Origin FAQ; TPCi Rules Team (2022-09-08)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH11_32
SWSH11_32