It seems like something changed and the Schedule Chime Meeting icon is no longer displayed
You can no longer schedule meetings for someone else from Outlook on Mac, there was a change to the experience after the macOS Outlook 16.42 client update.
We only support scheduling meetings for someone else using the Amazon Chime add-in for Outlook on Windows. Visit https://answers.chime.aws/articles/188/scheduling-a-meeting-for-someone-else-using-outloo.html
If you want to schedule a meeting for someone else and you use macOS. You can do the following:
View the Amazon Chime User, Administration Guide and API Reference on the AWS Documentation site.
Find more information about the Amazon Chime solution, pricing, customer references, getting started, and other resources.