Publishing Outlook add-in which uses Outlook preview element - SupportsSharedFolders

I am developing Outlook add-in which will work with shared mailboxes. Currently, office add-ins are not available on delegate scenarios but MS has released preview build which supports these scenarios. https://learn.microsoft.com/en-us/office/dev/add-ins/reference/manifest/supportssharedfolders

My problem is since the manifest.xml has preview elements; I can't upload the it at outlook.office365.com under my add-ins. I get following error.

This app can't be installed. The manifest file doesn't conform to the schema definition. The element 'DesktopFormFactor' in namespace 'http://schemas.microsoft.com/office/mailappversionoverrides/1.1' has invalid child element 'SupportsSharedFolders' in namespace 'http://schemas.microsoft.com/office/mailappversionoverrides/1.1'. List of possible elements expected: 'ExtensionPoint' in namespace 'http://schemas.microsoft.com/office/mailappversionoverrides/1.1'... The element 'DesktopFormFactor' in namespace 'http://schemas.microsoft.com/office/mailappversionoverrides/1.1' has invalid child element 'SupportsSharedFolders' in namespace 'http://schemas.microsoft.com/office/mailappversionoverrides/1.1'. List of possible elements expected: 'ExtensionPoint' in namespace 'http://schemas.microsoft.com/office/mailappversionoverrides/1.1'.

Anyone know any other way to deploy the add-in for users or even test it out without being to upload xml file?

Thanks in advance.

Copy of my manifest.xml file is here.

<?xml version="1.0" encoding="UTF-8"?>
<OfficeApp
          xmlns="http://schemas.microsoft.com/office/appforoffice/1.1"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xmlns:bt="http://schemas.microsoft.com/office/officeappbasictypes/1.0"
          xmlns:mailappor="http://schemas.microsoft.com/office/mailappversionoverrides"
          xsi:type="MailApp">

  <Version>1.0.0.0</Version>
  <ProviderName></ProviderName>
  <DefaultLocale>en-US</DefaultLocale>
  <DisplayName DefaultValue="Sample1" />
  <Description DefaultValue="First Sample Angular Add-in"/>
  <IconUrl DefaultValue="xxxx.jpg" />
  <HighResolutionIconUrl DefaultValue="https://localhost:3000/assets/hi-res-icon.png"/>

  <!--If you plan to submit this add-in to the Office Store, uncomment the SupportUrl element below-->
  <SupportUrl DefaultValue="https://localhost:3000/support.html" />

  <!-- Domains that will be allowed when navigating. For example, if you use ShowTaskpane and then have an href link, navigation will only be allowed if the domain is on this list. -->
  <AppDomains>
    <AppDomain>AppDomain1</AppDomain>
    <AppDomain>AppDomain2</AppDomain>
    <AppDomain>AppDomain3</AppDomain>
  </AppDomains>
  <!--End Basic Settings. -->

  <Hosts>
    <Host Name="Mailbox" />
  </Hosts>
  <Requirements>
    <Sets>
      <Set Name="Mailbox" MinVersion="1.1" />
    </Sets>
  </Requirements>
  <FormSettings>
    <Form xsi:type="ItemRead">
      <DesktopSettings>
        <SourceLocation DefaultValue="https://localhost:3000/index.html"/>
        <RequestedHeight>250</RequestedHeight>
      </DesktopSettings>
    </Form>
  </FormSettings>

  <Permissions>ReadWriteItem</Permissions>
  <Rule xsi:type="RuleCollection" Mode="Or">
    <Rule xsi:type="ItemIs" ItemType="Message" FormType="Read" />
  </Rule>
  <DisableEntityHighlighting>false</DisableEntityHighlighting>

  <VersionOverrides xmlns="http://schemas.microsoft.com/office/mailappversionoverrides" xsi:type="VersionOverridesV1_0">
    <Description resid="residDescription" />
    <Requirements>
      <bt:Sets DefaultMinVersion="1.3">
        <bt:Set Name="Mailbox" />
      </bt:Sets>
    </Requirements>
    <Hosts>
      <Host xsi:type="MailHost">
        <!-- add information on form factors -->
      </Host>
    </Hosts>
    <Resources>
      <!-- add information on resources -->
    </Resources>

    <VersionOverrides xmlns="http://schemas.microsoft.com/office/mailappversionoverrides/1.1" xsi:type="VersionOverridesV1_1">
    <Requirements>
      <bt:Sets DefaultMinVersion="1.3">
        <bt:Set Name="Mailbox" />
      </bt:Sets>
    </Requirements>
    <Hosts>
      <Host xsi:type="MailHost">

        <DesktopFormFactor>
          <!-- Location of the Functions that UI-less buttons can trigger (ExecuteFunction Actions). -->
          <FunctionFile resid="functionFile" />
          <SupportsSharedFolders>true</SupportsSharedFolders>
          <!-- Message Read -->
          <ExtensionPoint xsi:type="MessageReadCommandSurface">
            <!-- Use the default tab of the ExtensionPoint or create your own with <CustomTab id="myTab"> -->
            <OfficeTab id="TabDefault">
              <!-- Up to 6 Groups added per Tab -->
              <Group id="msgReadGroup">
                <Label resid="groupLabel" />
                <!-- Launch the add-in : task pane button -->
                <Control xsi:type="Button" id="msgReadOpenPaneButton">
                  <Label resid="paneReadButtonLabel" />
                  <Supertip>
                    <Title resid="paneReadSuperTipTitle" />
                    <Description resid="paneReadSuperTipDescription" />
                  </Supertip>
                  <Icon>
                    <bt:Image size="16" resid="icon16" />
                    <bt:Image size="32" resid="icon32" />
                    <bt:Image size="80" resid="icon80" />
                  </Icon>
                  <Action xsi:type="ShowTaskpane">
                    <SourceLocation resid="messageReadTaskPaneUrl" />
                  </Action>
                </Control>
                <!-- Go to http://aka.ms/ButtonCommands to learn how to add more Controls: ExecuteFunction and Menu -->
              </Group>
            </OfficeTab>
          </ExtensionPoint>
          <!-- Go to http://aka.ms/ExtensionPointsCommands to learn how to add more Extension Points: MessageRead, AppointmentOrganizer, AppointmentAttendee -->
        </DesktopFormFactor>
      </Host>
    </Hosts>
    <Resources>
      <!-- add information on resources -->
    </Resources>
    </VersionOverrides>
  </VersionOverrides>
</OfficeApp>

I've experienced the same issue today. I was able to solve it by moving the SupportsSharedFolders tag to the beginning of the DesktopFormFactor tag.

Instead of this:

...
<DesktopFormFactor>
  <!-- Location of the Functions that UI-less buttons can trigger (ExecuteFunction Actions). -->
  <FunctionFile resid="functionFile" />
  <SupportsSharedFolders>true</SupportsSharedFolders>
  <!-- Message Read -->
  ...

it should look like this

...
<DesktopFormFactor>
  <SupportsSharedFolders>true</SupportsSharedFolders>
  <!-- Location of the Functions that UI-less buttons can trigger (ExecuteFunction Actions). -->
  <FunctionFile resid="functionFile" />
  <!-- Message Read -->
  ...