Can we create custom activities and categories in StudioX?

We do support custom activities, but they would need to be tested before saying they are compatible. StudioX does not have the concept of defining complex types, only primitives such as Strings and Numbers. It can store any complex type output by an activity, but the user will not be able to define them (for e.g. if an activity expected the user to define an array as an input, this isn’t supported). For StudioX, the design philosophy is that users should not need to use the properties panel for any required properties unless they want to do some more advanced use cases. So, the designer of each activity should contain all they need for nearly all use cases.