ContextMenu

link - learn.microsoft.com/en-us/office/dev/add-ins/reference/manifest/officemenu

ContextMenuText - Excel, Word, PowerPoint. Displays the item on the context menu when text is selected and then the user right-clicks on the selected text.
ContextMenuCell - Excel. Displays the item on the context menu when the user right-clicks on a cell on the spreadsheet.

<ExtensionPoint xsi:type="ContextMenu"> 
  <OfficeMenu id="ContextMenuCell"> 
    <Control xsi:type="Menu" id="ContextMenu2"> 
            <!-- information about the control --> 
    </Control> 
    <!-- other controls, as needed --> 
  </OfficeMenu> 
</ExtensionPoint>