Hi sharp1907,
Thanks for posting in Apple Support Communities.
We understand you’d like easier/faster way to add multiple contacts to an email using your iPhone. This may take up some time to set up, but it will make sending an email to multiple contacts easier.
Use Contacts on iCloud.com - Apple Support -- With iCloud Contacts you can create an mange groups of Contacts. Then all you’d need to do on your iPhone is type the list you’ve created in the email address box.
To do so, you’ll need to export the Contacts directly from the email account(s) you’re using for Contacts on your iPhone: Import or export a vCard in Contacts on iCloud.com - Apple Support
As an example, here’s how you’d export a Gmail Contact: Export, back up, or restore contacts - Computer - Contacts Help
As we stated previously, this will take some time to set up. There isn’t any other way to easily add multiple contacts to an email on your iPhone. However, Apple does appreciate all feedback regarding our products, services, and features. If you'd like to provide feedback on your experience with our products or services, you can do so using this link: Feedback - iPhone - Apple
Regards.