The feature is not available yet but is on the roadmap for late July timeframe, 394687.
It's also been announced in the Message Center as MC798322:
Description
Coming soon to Microsoft Outlook: When updating meeting attendees, organizers will be prompted to send updates only to added or removed attendees or to send updates to all attendees. This message applies to Outlook for the web and New Outlook for Windows.
This message is associated with Microsoft 365 Roadmap ID 394687.
[When this will happen:]
General Availability (Worldwide): We will begin rolling out late July 2024 and expect to be complete by late August 2024.
[How this will affect your organization:]
Before the rollout, organizers who updated meeting attendees were not prompted with Send options.
After the rollout, the default state is on, and this feature will be available to all users.
[What you need to do to prepare:]
This rollout will happen automatically by the specified dates with no admin action required before the rollout. You may want to notify your users about this change and update any relevant documentation as appropriate.