When customizing page layouts in Salesforce, some standard related lists cannot be edited. This is expected behavior. Related lists on Custom Objects can always be edited, but certain standard related lists are locked and cannot be customized on any object.
For example, an admin customizing an Account page layout may find that the Account Team related list cannot be edited. This is expected behavior for certain standard related lists.
Some standard Salesforce related lists cannot be customized — this is working as designed. Related lists on Custom Objects can always be edited, but certain standard related lists (such as Notes & Attachments, Contact Roles, and Field History Tracking lists) are locked. The reference list below covers all known non-editable related lists by object.
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