Add a custom control to a container (see CONTAINER_* enum). There are many locations where custom controls can be added in the editor UI.
Please remember that you have to manage the visibility of your custom controls yourself (and likely hide it after adding it).
When your plugin is deactivated, make sure to remove your custom control with removeControlFromContainer and free it with queue_free().
Add a custom control to a container (see CONTAINER_* enum). There are many locations where custom controls can be added in the editor UI. Please remember that you have to manage the visibility of your custom controls yourself (and likely hide it after adding it). When your plugin is deactivated, make sure to remove your custom control with removeControlFromContainer and free it with queue_free().