Taskfeed 1.51 - Release Notes
New parameters on the TaskfeedBoard component 'RelatedRecordId' and 'RelatedRelationshipName' allow an administrator or developer to define the context of the Board. For example, when embedded into an Opportunity the RelatedRecordId would be {!Opportunity.Id} and the RelatedRelationshipName would be the name of the lookup field on the Task 'Opportunity__c'.
When a Taskfeed Task is created from this embedded context then the Task will automatically have the field defined as the RelatedRelationshipName populated with the value of RelatedRecordId.