Hi ! Yes you can definitely do that using a batched map call.
Basically you can return more examples than the number of examples in per batch:
from datasets import Dataset

d = Dataset.from_dict({"foo": [(1, 2, 3), (5, 7, 8)]})
d = d.map(lambda x: {"foo": [i for row in x["foo"] for i in row]}, batched=True)

print(d["foo"])
# [1, 2, 3, 5, 7, 8]