GoogleSlideで画像などに強調したい部分以外に半透明の図形を被せるアドオン

hightlight.js

function onInstall(e) {
  onOpen();
}

function onOpen(e) {
  SlidesApp.getUi().createAddonMenu()
    .addItem('Hightlight(Black)', 'highlightBlack')
    .addItem('Hightlight(White)', 'highlightWhite')
    .addToUi();
}

function highlightBlack() {
  highlight('#000000')
}

function highlightWhite() {
  highlight('#FFFFFF')
}

// ImageやShape上にあるtargetというテキストのShapeの範囲を強調する
function highlight(color) {
  const presentation = SlidesApp.getActivePresentation();
  const pageIndex = getTargetPageIndex(`Highlight ${color}`)
  const slides = presentation.getSlides();
  const slide = slides[pageIndex];

  const objects = [...(slide.getShapes().filter(s => s.getShapeType() !== SlidesApp.ShapeType.TEXT_BOX)), ...(slide.getImages()), ...(slide.getSheetsCharts())]
  const targetShapes = slide.getShapes().filter(s => s.getText().asString() === 'target\n')

  const cordinate = (s) => {
    return {
      top: s.getTop(),
      bottom: s.getTop() + s.getHeight(),
      left: s.getLeft(),
      right: s.getLeft() + s.getWidth()
    }
  }
  const isBehind = (shape, object) => {
    const front = cordinate(shape)
    const back = cordinate(object)

    // frontがbackに内包されている状態
    if (front.top > back.top && front.bottom < back.bottom && front.left > back.left && front.right < back.right) {
      return true
    }
    return false
  }

  targetShapes.forEach(s => {
    const behindObject = objects.find(o => isBehind(s, o))

    const lefts = [
      behindObject.getLeft(),
      s.getLeft(),
      s.getLeft() + s.getWidth()
    ]
    const tops = [
      behindObject.getTop(),
      s.getTop(),
      s.getTop() + s.getHeight()
    ]
    const widths = [
      s.getLeft() - behindObject.getLeft(),
      s.getWidth(),
      (behindObject.getLeft() + behindObject.getWidth()) - (s.getLeft() + s.getWidth())
    ]
    const heights = [
      s.getTop() - behindObject.getTop(),
      s.getHeight(),
      (behindObject.getTop() + behindObject.getHeight()) - (s.getTop() + s.getHeight())
    ]

    const hatchShapes = [[true, true, true], [true, false, true], [true, true, true]].map((line, i) => {
      return line.map((item, j) => {
        if (!item) {
          return false
        }

        const hatchShape = slide.insertShape(
          SlidesApp.ShapeType.RECTANGLE,
          lefts[i],
          tops[j],
          widths[i],
          heights[j]
        )

        const fill = hatchShape.getFill()
        fill.setSolidFill(color, 0.4)
        const border = hatchShape.getBorder()
        border.setTransparent()

        return hatchShape
      }).filter(v => v)
    }).flat()

    slide.group(hatchShapes)
    s.remove()
  })
}