How to activate a Quick Create Form in Opportunity for Opportunity Products and Quotes

Hi everybody,

I really need your help on this. As mentioned in the subject line, I want to provide Quick Create Forms for "Quotes" and "Opportunity Products" within the Opportunity Entity. I've already marked the check box "Allow quick create" in both entities(Quotes/Opportunity Products) and also created the necessary Quick Create Forms. I've also set the Field Requirement in the 1:N relationships for both entities within the Opportunity Customization to "Business required" to prevent the look up line from appearing when using the "+" button in the subgrid. Furthermore I've added two new subgrids to the Opportunity. One for Quotes and one for Opportunity Projects.

So, neither with the out-of-the-box subgrids nor with my newly added ones am I able to force the Quick Create Form to appear for these two entities. I also have two other subgrids on my Opportunity Form for custom entities and these work just perfectly. What am I doing wrong? One last thing: I have a subgrid for Quotes on my Account Form and if I use the "+" Button to create a new one...voilá, the Quick Create Form appears. Only on the Opportunity Form the Quick Creation refuses to appear.

Thanks you in advance for your help.