How to append a new data block with new-line in red?

Question

I tried:

data: [a b c]
new-line tail data true
append data [d e f]

I get

[a b c d e f]

not what I expect:

[a b c 
d e f]

Answer 1

Newline marker is a property of a value slot, not of a series. new-line tail data true didn't set this marker, because tail of a series does not contain any value slot (but back tail does).

>> head new-line tail [a b c] on
== [a b c]
>> head new-line back tail [a b c] on
== [a b 
    c
]
>> append [a b c] new-line [d e f] on
== [a b c 
    d e f
]