How to save a group in my iMessages?

How to save a group in my messages ap so I can repeatedly send to the same people in this group without having to re-type names each time. I looked it up, but I don't get the "save group" option to click at the bottom of the details window. Here's the instructions I get:

Add a group name and photo

You can send a message to a group of people, then name your group conversation so that it’s easier to keep track of and find.

1. In the Messages app on your Mac, select a group conversation.
2. To search for contacts and content in conversations, click in the Search field in the top-left corner and enter what you’re looking for. Or, choose from the suggested contacts, links, photos, and more.
3. Click the Details button , click “Change Group Name and Photo,” then follow the onscreen instructions.

• • Group Name: Enter the group name as you want it displayed.
  • Photo: Choose anything from a colorful monogram, a standard photo, or a personalized Memoji.

1. Click Done.

[Re-Titled by Moderator]