My response which I sent to you via email:
I think that WordPress automatically uses Responsive Images when images are inserted within the main editor (content) of a WordPress post type. When creating a post type within WordPress (e.g. portfolio, product, testimonial), you normally enable this main editor within your custom post type – but you can elect to disable this main editor if you want when you create a post type.
With Slide Anything, I disabled this main editor, because I need a separate editor for every slide within a slider, and the main editor pertains to the custom post as a whole, which is the Slide Anything slider.
So I used the WordPress ‘wp_editor()’ function (https://codex.ww.wp.xz.cn/Function_Reference/wp_editor) to create an editor for EACH slider within the slider, which works pretty much like the main post editor with regards to functionality. I don’t see anything within the documentation options for ‘wp_editor()’ regarding responsive images, so I assume that WordPress has not built this functionality into this function, or have not got around to doing it yet.
