You no longer have to forward multiple mails within an email as Gmail's latest update will help you send an email within another one as an attachment.
As the official blog notes, users will be able to attach emails to other mail, without the prior having to download them first.
Now, to do so you can follow the following steps. On your computer, go to Gmail, select the emails that you want and click 'More' and then 'Forward as attachment'. In the 'To' field, add recipients. You can also add recipients in the “Cc” and “Bcc” fields. Add subject, message body and then click send!.
Meanwhile, to attach emails in a reply, while perhaps you’re maintaining the same thread or such you can do the following-
On your computer, go to Gmail and open the email and click Reply. At the top right of the email, click the Pop out icon, then from your inbox, select the email you want to attach. Drag the email into your message and click Send.
The roll out for the update will begin from the 16th of December, and ‘gradually’ across all g-suite editions, according to the blog. Users will have this feature offered to them, automatically updated.