↓ — Split / Drop↓Y nests vectors along the last axis.
↓2 3⍴⍳6 ⍝ (1 2 3)(4 5 6)
N↓Y drops from the front; negative N drops from the end.
2↓1 2 3 4 ⍝ 3 4
¯2↓1 2 3 4 ⍝ 1 2
[K] selects the split axis or drop axes.
↓[1]2 3⍴⍳6 ⍝ (1 4)(2 5)(3 6)
Vector counts apply to successive leading axes. Overdrop gives an empty axis.
1 1↓2 3⍴⍳6 ⍝ 1 2⍴5 6
5↓1 2 ⍝ ⍬
See Mix / Take.