Detach and flatten all frames in Figma

detach.js

const detachAndFlatten = (pageName) => {
  const detach = (c) => figma.union([c], c.parent)
  const page = figma.root.children.find(c => c.name === pageName)
  const frames = page.children.filter(c => c.type === "FRAME")

  for (let frame of frames) {
    for (let c of frame.children) {
      if (c.type === "INSTANCE") {
        c = detach(c)
      } else {
        //
      }
      figma.flatten([c])
    }
  }
}

Usage

1. Open the console in Figma
2. Paste the code
3. type detachAndFlatten("here is your page name")