Many to Many Relationship: Bulk Import?

I have a custom module “Properties.”

It has a Many:Many relationship with Leads.

I want to be able to bulk update or bulk import Leads and attach a property to them.

It seems that the import tool only adds a $Related_Field ID if a one:many relationship exists.

Is there any way around this?

It is not possible to import relational data of many to many. To achieve it you need to create an import script to set relational data as well.