CRM 2016:How to change the behavior of the add opportunity product button to open directly the opportunity product window?

Hello,

I have tried almost all solutions to open directly the opportunity product window when the user clicks on the plus button from the opportunity form.

I have changed the default grid ,changed the view, ticked in system setting the "use legacy forms" and none worked. What is weird is that the plus button on the quote product grid in the quote form directly opens the form. Any idea what to do?

Thanks.