Hi
Is there any out of box functionality to book appointment via a calendar interface on partner portal.

Hi
Is there any out of box functionality to book appointment via a calendar interface on partner portal.
Its quite complex what you are trying to achieve.
You will need to get all the free booking slot times in CE using this action docs.microsoft.com/.../msdyn_retrieveresourceavailability
You should create a custom entity to support the creation of these records. You can then expose these to a calendar view within a portal. Then the customer can choose a free booking slot time on the calendar to book from