write

If write is false, then this item won't be rendered. You can use it for example for hidden guis. Also look to locate

Yaml:

- write: false
  stack: STONE # you never see this
  id: myContainer
  items: # you can open this with locate variable
  - STONE

Groovy: Because this variable is not needed with true (that's default), only with false, we have special structure for this in Groovy.

hidden('myContainer') /* <-- This is an id*/ {
  /* Here can be just items */
  item('STONE')
}