There is nothing in the schema itself that indicates possible values from data. There's actually no requirement that items in the required array also be defined in properties.

This sort of functionality is defined by the IDE only. IntelliJ IDEA documents the ability to add custom schemas:

Besides schemas from JSON Schema Store, IntelliJ IDEA lets you configure and use custom schemas from other storages. You can download the required schema and store it under the project root or specify the URL of the resource so IntelliJ IDEA can download the schema automatically.

To configure a custom JSON Schema:

In the Settings/Preferences dialog ⌘,, go to Languages and Frameworks | Schemas and DTDs | JSON Schema Mappings.

https://www.jetbrains.com/help/idea/json.html#ws_json_schema_add_custom

It also details later how to make the intelesense provide a rich preview:

Using HTML descriptions in JSON schema #

By default, IntelliJ IDEA escapes HTML characters when displaying documentation for JSON schema definitions in documentation popups. To get nice looking documentation with rich HTML markup, store the HTML description in the x-intellij-html-description extension property instead of description.

https://www.jetbrains.com/help/idea/json.html#ws_json_show_doc_in_html

However,

autocompletes based on another properties' keys

sounds like custom functionality specifically designed for writing JSON Schema. JSON Schema itself cannot reference data dynamically like that (which I assume is what you were thinking).