Here are two options:
Open the meeting in the calendar view and click on the scheduling assistant button - this lists all invitees with their required/optional status
Add some custom formatting to show optional meetings visually.
- Right click on the calendar
- Select "View Settings"
- Select "Conditional formatting"
- Add a new rule, give it a name and a colour of choice
- Select "Condition" and then "Advanced"
- Click "Field", select "All appointment fields" and then "Optional attendees"
- Set the condition to "includes" and the value to your name.
- Optional appointments should then show up in a different colour.