This add in collapses all rows to give you a high level reading view.

Collapse Rows.EXCEL.yaml

name: Collapse Rows
description: This add in collapses all rows to give you a high level reading view.
host: EXCEL
api_set: {}
script:
  content: |
    $("#collapseRows").click(() => tryCatch(run));

    async function run() {
      await Excel.run(async (context) => {
        const sheet = context.workbook.worksheets.getActiveWorksheet();
        var usedRange = sheet.getUsedRange(false);

        usedRange.load("rowCount, format");
        await context.sync();

        var lastRow = usedRange.rowCount;
        console.log("Total rowCount:" + lastRow);

        var firstRow = $("#startRow").val();
        console.log("Starting row:" + firstRow);

        var selectRange = sheet.getRange(firstRow + ":" + lastRow);

        var height = $("#rowSize").val();
        console.log("desired row height:" + height);

        selectRange.format.rowHeight = Number(height);
        console.log("changed row height:" + selectRange.format.rowHeight);
      });
    }

    /** Default helper for invoking an action and handling errors. */
    async function tryCatch(callback) {
      try {
        await callback();
      } catch (error) {
        // Note: In a production add-in, you'd want to notify the user through your add-in's UI.
        console.error(error);
      }
    }
  language: typescript
template:
  content: "<section class=\"ms-font-m\">\n\t<p class=\"ms-font-m\">This sample demonstrates how to use this addin using Excel API calls.</p>\n</section>\n\n<section class=\"samples ms-font-m\">\n\t<h3>Try it out</h3>\n\t<p class=\"ms-font-m\">Go to the worksheet where you want to have a high level view and, then press button\n\t\t<b>Collapse Rows</b>.</p>\n\t<button id=\"collapseRows\" class=\"ms-Button\">\n        <span class=\"ms-Button-label\">Collapse Rows</span>\n    </button>\n\t<input type=\"number\" id=\"rowSize\" value=12>Enter Row height (default=12)</input>\n\t<br>\n\t<br>\n\t<input type=\"number\" id=\"startRow\" value=3>Specify Start Row (default=3)</input>\n\t<img src='https://laughtard.com/wp-content/uploads/2017/06/gif-12-4.gif'>\n</section>"
  language: html
style:
  content: |-
    section.samples {
        margin-top: 20px;
    }

    section.samples .ms-Button, section.setup .ms-Button {
        display: block;
        margin-bottom: 5px;
        margin-left: 20px;
        min-width: 80px;
    }
  language: css
libraries: |
  https://appsforoffice.microsoft.com/lib/1/hosted/office.js
  @types/office-js

  office-ui-fabric-js@1.4.0/dist/css/fabric.min.css
  office-ui-fabric-js@1.4.0/dist/css/fabric.components.min.css

  core-js@2.4.1/client/core.min.js
  @types/core-js

  jquery@3.1.1
  @types/jquery@3.3.1