Subgrid open specific form pass parameters

I have a question on subgrids and opening a specific form via clicking the + from the subgrid and passing parameters

I use the contact and case entities

on the contact form is the standard form,  on the case I have 2 forms ( one is the standard information case form, the other is a custom case summary form)

when opening a case form, if I was on the case summary form last time i opened a case form, that would be the form that opens  by default (this seems to be a microsoft CRM Out of box function)

my issue is that from my contact record I call the case entity via a subgrid and when I click the + I want to open a new case but go to a specific form only and pass paramaters from contact to case

 I have the custom JS to call the specific form via form ID but I am having trouble finding out how to modify the + of the case subgrid via ribbon workbench

again i want to modify the + of a case subgrid to call a specific form and pass parameters from contact

how do I do this can someone detail the process in the ribbon workbench or a better way

Thanks