ribbon.xml

<?xml version="1.0" encoding="UTF-8"?>
<customUI xmlns="http://schemas.microsoft.com/office/2009/07/customui" onLoad="Ribbon_Load">

  <ribbon>

    <tabs>
      <tab idMso="TabAddIns" label="Docxmerge">
        <group id="ContentGroup" label="Template actions">
          <button id="textButton" label="Upload"
                  screentip="Text" onAction="OnTextButton"
                  supertip="Inserts text at the cursor location."/>
          <button id="tableButton" label="Insert Table"
                  screentip="Table" onAction="OnTableButton"
                  supertip="Inserts a table at the cursor location."/>
        </group>
      </tab>
    </tabs>
  </ribbon>
  <backstage onShow="Backstage_OnShow" onHide="backstageOnHide">
    <tab idMso="TabRecent">
      <firstColumn>
        <taskFormGroup idMso="GroupOpenPlaces">
          <category idMso="ButtonCategoryRecentDocuments">
            <task id="myTaskFirst" insertAfterMso="ButtonTaskRecentDocuments" label="Docxmerge">
              <group id="myGroup" label="Custom functionality" helperText="This group contains custom functionality.">
                <primaryItem>
                  <button id="myButton" label="Login with Docxmerge" onAction="CallLogin"/>
                </primaryItem>
              </group>
            </task>
          </category>
        </taskFormGroup>
      </firstColumn>
    </tab>

    <!--<tab idMso="TabPrint" label="BackstageTab1" visible="false" />-->
  </backstage>
</customUI>