Configure the Call, Task, and Event Tabs in the Activity Composer in Lightning Experience | Salesforce
Is the call, task, or event tab missing from the activity composer on opportunities or other objects in your Salesforce org? Check your layout, record type, and permissions settings.
|Available in Lightning Experience in: Professional, Enterprise, Performance, Unlimited, and Developer Editions|
Look at the object’s page layout—opportunities, leads, accounts, contacts, or a custom object that supports activities. Check whether you’ve included the corresponding action in the Salesforce1 and Lightning Experience Actions section of the object’s page layout.
An object page inherits the actions of the global page layout unless you’ve customized the actions in the Salesforce1 and Lightning Experience Actions section of the object’s page layout.
Have you created a custom record type for calls, tasks, or events? (Record types determine a record’s layout and picklist values. You can define one or more record types for users to choose from when they create an event or a task.) Look at the page layout that you’ve associated with the custom record type. Ensure that you’ve assigned the custom record type to the corresponding action. For example, if you created a custom record type for calls, assign it to the Log a Call action.
Ensure that your users have permission to view that custom record type.