In our system, some contacts are linked to the leads later in the process, therefore those contacts don't have the Originating Lead (originatingleadid). Also, we want to connect some contacts to multiple leads.
Currently, we are connecting contacts and leads through the Parent Contact for Lead field (parentcontactid in lead entity).
But the problem is that if the contact does not have an Originating Lead, the activities from the lead are not displayed in the contact's social pane. The relation made through parentcontactid field is ignored.
Is there any workaround for this? Is it possible to make such a relation between the contact and the lead that the activities from the lead are displayed in the contact's social pane?
The originatingleadid field is not valid for update, it can be set only on create.
You can change the Rollup View Relationship Behavior on custom 1:N relationships to Cascade All. In this way the activities from children will be shown on the activity view for the parent.
This would require you to create a custom relationship between Contact and Lead, since you cannot change this property on the standard relationships in the system.
You have not specified a version. The Rollup View Relationship Behavior was added in Dynamics 365 (version 8.2).