B.E. to insert Task Template to Cases

hello, I created an attribute for a Case class.
When activated (attribute) the CaseCD appears in a G.I.
The goal is to automatically add multiple Task Templates in the Case if this attribute is enabled.

However in Task Template we must point the shape type (Case).
In the business event, I point my G.I. in the header, this therefore does not allow me to add the Case Template since it does not recognize my GI as being the CASE form.

How to get there?
I would like not to have to create a case class for this

Thanks!