Set Parent Object Relationship Field

[DanDonin]

We can set the Child Object relationship field and the tool assumes it relates to the Parent via the Parent.Id being held in the relationship field. What about if your Child is related to the Parent object via an External id field. So I have an External Id field on my Parent Object and an External Id field on my child and I want them to relate via that field.

Would there be a way to more or less have an "override" so you could define the field on the Parent side? And tell the Tool to use the external Id as the relationship between the two objects?

Example

Parent = Object1 Object1.External__c

Child = Object2 Object2.External__c

Now here the Child Object2 doesn't have a Lookup or a String of the Object1 Id. It does have the External__c that matches to the Parent object but not via the Object1.Id but via the Object1.External__c.

So I'd tell DLRS my Parent is Object1 and my Child is Object 2 the relationship field is External__c but I need a way to tell it that the Parent is located via External__c on the parent and not the Id of the parent.