.h.cd x

Where x is a table or a list of columns returns a matrix of comma-separated values.

q).h.cd ([]a:1 2 3;b:`x`y`z)
"a,b"
"1,x"
"2,y"
"3,z"

q).h.cd (`a`b`c;1 2 3;"xyz")
"a,1,x"
"b,2,y"
"c,3,z"

Columns can be nested vectors, in which case .h.d is used to separate subitems. (Since V4.0 2020.03.17.)