The Problem

At the moment, //chunk only selects 256-block tall "sections" (not actual chunk sections) aligned starting from y=0. As seen in #2038, it might be useful to allow selecting smaller or larger vertical heights, potentially from actual chunk sections (16 blocks) to the entire world height (potentially up to 4096 blocks, or more if mods extend MC's limits).

A Solution

Flags could be added to the //chunk command to allow selecting chunk sections, full world height, or potentially some arbitrary number in between (though see additional context for potential issues on alignment - might want to make multiple of 16 mandatory?).

Alternatives

Just use //expand vert or any other combination of //expand///contract after running //chunk.

Anything Else?

my ramblings from discord:

a) selecting everything by default is bad - it means potentially selecting 400 to 4000 blocks the user is unaware of.
b) chunks should have a well-defined alignment vertically (as they do horizontally. imagine if the origin chunk was x/z -7 -> 9 instead of 0->15 arbitrarily) . chunk sections (the 16^3 ones) are a good default alignment, but are too small, so we default to the old alignment of 0-255.
c) using default-vertical-height would be ok except it still doesn't make sense with "default" MC settings since even if you increase it to 512 the first aligned chunk would be 0->511, not (-64->448 which hits the default min y, but is too high; or -128 -> 384 which hits the default max y, but is too low)