Add 'Primary Campaign Source' field on Opportunity List View

This is working as designed, however there is a workaround available.

Add the 'Primary Campaign Source' field on an Opportunity List view.

In Salesforce Classic:

1. Click Setup.
2. Click Customize.
3. Click Opportunity 
4. Select Field.
5. Click New field | Select Data Type Formula | Return type Text 
6. Add the following as the syntax:  Campaign.Name 
7. Click Save.
8. Add the custom Formula field to an Opportunity List View.

In Lightning Experience

1. Click Setup.
2. Click on Object Manager. 
3. Click Opportunity. 
4. Click Fields & Relationships.
5. Click New button. 
6. Click New field | Select Data Type Formula | Return type Text 
7. Add the following as the syntax:  Campaign.Name 
8. Click Save.
9. Add the custom Formula field to an Opportunity List View.

Steps to add the formula field in opportunity list view in Lightning Experience (LEX):

1. Click on Opportunity tab. 
2. Open the list view 
3. Click on wrench icon next to the list view name
4. Click on Select Fields to Display
5. Add the Custom Formula Field
6. Save. 

Notes:

• This same behavior is also observed when attempting to add Primary Campaign Source to a Search Layout:
  • In Classic or LEX, navigate to the Opportunity Entity in Setup
  • Go to Search Layouts
  • Edit the Search Result layout
  • Try to look for the Primary Campaign source field among the list of Available Fields
  • Result: you'll not see it
• This field can be from the record Page Layout and still make this field Visible in Field level Security permissions.