In the IDE, the Object Inspector lets you selectively hide and display properties based on property categories. The properties of new custom components can be fit into this scheme by registering properties in categories. Do this at the same time you register the component by calling RegisterPropertyInCategory or RegisterPropertiesInCategory. Use RegisterPropertyInCategory to register a single property. Use RegisterPropertiesInCategory to register multiple properties in a single function call. These functions are defined in the unit DesignIntf.
Note that it is not mandatory that you register properties or that you register all of the properties of a custom component when some are registered. Any property not explicitly associated with a category is included in the TMiscellaneousCategory category. Such properties are displayed or hidden in the Object Inspector based on that default categorization.
In addition to these two functions for registering properties, there is an IsPropertyInCategory function. This function is useful for creating localization utilities, in which you must determine whether a property is registered in a given property category.