Proposal to allow creating a field and setting its value in one go

I always find it very tedious to first enter a field name, click "add" (could you add "Return" here as a shortcut?) and then to click the newly created field to enter the value. Especially when an instruction shows field and value like this: "field: value".

This proposal splits a field name at the first colon and sets the name to be the left and the new value to be the right part.
I differ at least on the "Rule of Readability".
I don't know what "Composability" means.
I did not pre-optimise, I simple wrote it in a natural way - at least natural for me programming for 34 years now.
KISS - I can't imaginge what's more simple than cutting strings at a found position.

But to be honest: Would the split operator in javascript work like the perl one I would have written it like this (in perl):

my($name, $value)= split /\s*:\s*/, $name, 2;

or without split:

my($name, $value)= $name=~ /^\s*(.*?)\s*:\s*(.*?)\s*$/;

which would have saved me the trims