Cannot see the 'phone' and 'email' fields on Tasks or Events in Lightning Experience

Overview of the Workaround

The following steps describe how to create custom lookup fields, formula fields, and a Salesforce Record-Triggered Flow to display Contact or Lead Phone and Email values on Tasks and Events in Lightning Experience.

Step 1: Create Custom Lookup Fields on the Activity Object

Create two custom Lookup fields on the Activity object — one for Contact and one for Lead.

• Field Name: cCntct__c | Data Type: Lookup(Contact)
• Field Name: cLead__c | Data Type: Lookup(Lead)

Step 2: Create Formula Fields to Capture Phone and Email

Create two custom formula fields on the Task or Event object to capture Phone and Email from the Contact or Lead lookup field.
Email formula: Case(LEFT(WhoId, 3), '00Q', cLead__r.Email, '003', cCntct__r.Email, 'Other')
Phone formula: Case(LEFT(WhoId, 3), '00Q', cLead__r.Phone, '003', cCntct__r.Phone, 'Other')
These formulas check the WhoId prefix to determine whether the related record is a Lead (prefix 00Q) or a Contact (prefix 003) and return the appropriate Phone or Email value.

Step 3: Create a Salesforce Record-Triggered Flow

Go to Setup, search for Flow, and click New Flow. Select Record-Triggered Flow and click Create. Configure the flow as follows:

• Flow Type: Free-Form
• Object: Task (repeat separately for Event)
• Trigger: A record is created or updated
• Condition Requirements: None
• Optimize for: Actions and Related Records

Add an Assignment element (label: RecordAssign) to assign the WhoId value to a Text variable named RecordCheck.
Add a Decision element (label: Lead OR Contact) with two outcomes:

• Lead outcome: RecordCheck starts with 00Q
• Contact outcome: RecordCheck starts with 003

Add Update Records actions for each outcome to populate cCntct__c or cLead__c with the RecordCheck value. Save and activate the flow. Create a similar flow for Event records.

Important Limitation

This field update action copies Phone and Email values from the first associated Contact record only. If a Task has 10 Contacts associated through the Name field, only the first Contact's Phone or Email is copied.

See Also:
Idea Exchange: Include Contact/Lead Phone and Email on Task Detail in Lightning Tasks page