It's not really related to this particular PR, it's more about question that bothers me :) Why don't we use something like this for such enum-like cases:

const composerLayout = {
  DEFAULT(or whatever is more suitable here): '',
  COMPOSER: 'composer',
  THREAD: 'thread'
}

It's more verbose of course, but doing so we can organize related strings into single 'group', add group comment and probably item-level comments where it's appropriate. Adding Julien too @julienw