Want to update multilevel Dictionary

Where is this stored?  Under what context will it be getting updated?  What have you tried?

it is stored in a local variable,

and the milestone data is unsorted, so i created a new list of sorted data.

a!localVariables(
  local!map: a!map(
    success: true,
    statusCode: 200,
    body: {
      cobMstrld: "CONB100227",
      onBoardingStatus: "IN_PROGRESS",
      milestones: { { id: 1 }, { id: 2 }, { id: 3 } }
    }
  ),
  local!body: local!map.body,
  local!updatedMilestones: { { id: 4 }, { id: 5 }, { id: 6 } },
  a!update(
    local!map,
    "body",
    a!update(
      local!body,
      "milestones",
      local!updatedMilestones
    )
  )
)