As per your issue description, I understand that you would are looking for an option to forward multiple emails at once in New Outlook.
I would like to inform you that, in New Outlook, currently the option to forward option is not available to forward multiple emails at once, which is available in classic Outlook. This option is still under development for future updates for New Outlook. However, we do not know the ETA of the feature to be rolled out in the future updates. Please make sure you keep your Office and new Outlook up to date to take advantage of feature updates as well as product corrections.
The workaround is to forward the emails by including them as attachments in an email by following the steps below.
1. Select the emails that you want to forward.
2. Click on New mail > Mail.
3. Drag and drop the selected emails to the new email. You should see that emails are added as attachments.
4. Now you can send this email to the recipient.
Note: The emails that are attached are in .eml format and hence, can be opened only within Outlook or Windows Mail app.
As this is an early preview of the new Outlook, not all functionality from classic Outlook for Windows is available yet. We are working on adding more aspects, for more details you can refer to the link: https://techcommunity.microsoft.com/t5/outlook-blog/things-to-know-about-the-new-outlook-for-windows/ba-p/3383964
Regards,