Custom 404 & error pages

Hi

I am looking to create custom error pages on my site without the use of theme-builder or an additional plugin.

I saw in the below referenced post, that GP are working on a way to edit the 404 page directly “in the next update”;

[https://generatepress.com/forums/topic/customizing-404-page/#post-1406399]

When is such an updated anticipated for release?

Also, is this planned for just editing the 404 page or all custom error pages?

Many thanks