Select View > Hide Activity Pane.
Drag the right edge of the Activity sidebar to the left until it disappears.
Here are some things to keep in mind:
The activity list includes activities made in the presentation within at least the last 30 days, including your own. It highlights only the latest activities by others.
Newly added participants can see the entire collaboration history in the activity list (going back at least 30 days).
In a public presentation (a presentation with access set to “Anyone with the link” and permission set to “Can make changes”), participants marked as “Guest” in the activity list and in notifications haven’t signed in to iCloud.
Any comments attributed to “Somebody” were made by participants who made their comments and then opted out of the presentation.
You can see what participants in a shared presentation are doing in real time. In the presentation, each participant appears as a cursor or highlight in a specific colour, which matches the colour next to their name in the participant list.
Turn notifications on or off to see when someone joins, edits or comments.
You can also show or hide participant cursors and activity highlights.
Click Done.
If you aren’t getting notifications, you may need to allow notifications for the Keynote app. Choose Apple menu > System Settings, then click Notifications in the sidebar. (You may need to scroll down.) Click Keynote, then turn on Allow notifications.