A Google Slides app script that skips/unskips slides based on the user's input

UnskipByNumbers.gs

function onOpen() {
  SlidesApp.getUi()
    .createMenu("Scripts")
    .addItem("Skip/Unskip by Numbers", "unskipByNumbers")
    .addToUi();
}

/** Prompts the user for slide numbers. Unskips all of the specified slides. Skips the rest. */
function unskipByNumbers() {
  var ui = SlidesApp.getUi();
  var response = ui.prompt("Enter slide numbers to unskip (all others will be skipped), separated by commas and/or whitespace:");
  if (response.getSelectedButton() !== ui.Button.OK) {
    return;
  }

  // Get the slide numbers to unskip in descending order numerically.
  // Subtract 1 from each slide number to convert from 1-based index to 0-based index.
  var toUnskip = response.getResponseText().split(/[\s,;]+/g).map(s => parseInt(s) - 1).filter(n => !isNaN(n));
  toUnskip.sort((a, b) => b - a);
  Logger.log(toUnskip);

  var slides = SlidesApp.getActivePresentation().getSlides();
  for (var i = 0; i < slides.length; ++i) {
    // The next slide to unskip will always be the last one in `toUnskip`.
    // If `toUnskip` is empty, all remaining slides should be skipped.
    if (toUnskip.length && i === toUnskip[toUnskip.length - 1]) {
      slides[i].setSkipped(false);
      toUnskip.pop();
    } else {
      slides[i].setSkipped(true);
    }
  }
}