Public custom states - is there something?

[mnezaikin.subs]

[New Feature] Reusable Element Properties

Hi everyone! We’re excited to share that reusable elements now come with customizable properties, making it so that a single reusable element can be repurposed in many ways. With this added flexibility, your library will be easier to maintain — you may even notice opportunities to consolidate some of your existing reusable elements! Instead of having a fixed data type attached to your reusable element, you can set up properties to assign dynamic data, including page-level data. You can set up …

You are talking about this, right?
Is this in beta yet? Because I can’t find properties of reusable elements in my editor

Upd. Found inside of the reusable element. Will check it out, thanks!