The definition of a custom panel and controls is a set of graphical user interface (GUI) elements that allow users to interact with a program or system. Custom panels and controls are designed to be user-friendly and intuitive, making it easier for users to navigate the system and access the features they need. Custom panels and controls can be used to create custom menus, buttons, sliders, and other elements that can be used to customize the user experience. Custom panels and controls can also be used to create complex forms and data entry fields, allowing users to quickly and easily enter data into the system. Custom panels and controls are a great way to create a unique and tailored user experience, allowing users to interact with the system in a way that is most comfortable for them.