Is it permissible to say: "O Allah, bless Muhammad and the family of Muhammad as You blessed Ibrahim and the family of Ibrahim, and grant favor to Muhammad and the family of Muhammad as You granted favor to Ibrahim and the family of Ibrahim in all the worlds, for indeed, You are Praiseworthy and Glorious" after the Tashahhud in prayer or in general, and is it permissible to add "in all the worlds"?

The wording "O Allah, bless Muhammad, the unlettered Prophet, and the family of Muhammad" is authentically established from the Messenger of Allah, may Allah bless him and grant him peace. It is preferable to adhere to the established forms of sending blessings upon the Prophet within the prayer. Outside of prayer, the matter is broader, but adhering to what the Prophet taught his companions is more befitting.