There are some property start with
_ of table component or other component, such as
_defaultFilters of table component.
I have used it in my develop, but we can't access it in editor nor these properties show in the official docs.
Should I rely on this properties, it was a normal api? will it change without notification in the future?
Since they are not part of the public interface, developers can change them at will without effecting the users of the interface.
Now in the case of JS and these not being private, we are free to use them, but just assume they will break at some point.
As @bradlymathews mentioned these are private variables that can and will change without notice. There's not much we can do to prevent you from accessing them, but we urge you to not write critical logic that depends on their current behavior.
We are absolutely committed to backwards compatibility for all non-underscored properties.