Page Template permission settings

Hi,

Please help me to set Page Template permissions. A user who is loggged as a designer role should only be able to create, modify and delete Page Templates (The option available under Design menu on top).
I could change Widget Template and Responsive-and-mobile-design permissions only to designers. But I couldn't find an option to change Page Templates permissions. I'm using 5.1 version.
Anyone please help me to do this..

Thanks in advance