Important Issues and PRs:

• Add an Icons block #16484
• SVG Icon registration API  #72215
• New Block: Icon Block #71227

We have stabilized three core features and shipped them in 7.0 Beta1:

• WP_Icons_Registry class: The singleton class that loads core SVG icons from a manifest file, stores them, and exposes methods to check registration and retrieve icon data and content. There is currently no way to register a custom icon.
• WP_REST_Icons_Controller: The REST API controller that exposes the icon registry over wp/v2/icons, letting the editor list icons and fetch a single icon by name.
• Icon block (core/icon): The core block that retrieves a list of icons from the endpoint and lists them in a modal. The selected icon name is saved as an attribute, and the content is rendered server-side via the icon registry.

To make the Icon API more robust and extensible, I believe the following features are necessary:

Icon registry enhancements

• Create public APIs (ref): I think we need APIs like the one below to allow consumers to filter the core icons and submit custom icons.
  • register_icon() function
  • unregister_icon() function
  • core-icons theme support: This is similar to the core-block-patterns theme support: if this support is disabled, all core icons will not be registered.
• SVG sanitization (ref): There is no core function to properly sanitize SVGs, so a class method currently does the job, but it is not perfect, and there is room for improvement. See #75550 for more details. Maybe we could create a core function like sanitize_svg() instead.
  Icons Registry: improve SVG sanitizer #75550
• Icon namespace validation (ref): Currently, custom icon registration is not allowed, and the namespace is hardcoded as core/. If we allow custom icon registration in the future, we will need to strictly check that the icon name follows the {namespace/icon-name} format.
  Icons: Enforce strict name validation in register method #76079

REST API enhancements

• Search based on keywords: The current endpoint allows us to filter icons by the search parameter, but only the name field is referenced. We could also reference the label field and an optional keywords field. Icons API: Support searching in labels; extend classes post-7.0 work #75878

Category Support

Similar to block patterns, it should be possible to support categories: consumers will want to group icon sets based on their own brand.

• Create a registry like WP_Icon_Categories_Registry
• Create an endpoint like WP_REST_Icons_Categories_Controller
• Create public APIs:
  • register_icon_category() function
  • unregister_icon_category() function

Collection Support

Similar to Font Library, it should be possible to support collection: consumers will want to group icon sets based on their own brand.

• Create a registry like WP_Icon_Colloections_Registry
• Create an endpoint like WP_REST_Icons_Colloections_Controller
• Create public APIs:
  • wp_register_icon_collection() function
  • wp_unregister_icon_collection() function
  • _wp_register_default_icon_collections function

Create Icon Picker Modal component

• To avoid increasing bundle size, the initial implementation built a custom picker without using DataViewPicker. (ref) Perhaps it should be possible to add a component like IconPickerModal to the @wordpress/block-editor package and load it from a block. This icon picker should be useful for blocks other than the Icon block as well.
  • DataViewsPicker based UI
  • Filter icons by category
  • Icons: Move IconPickerModal into block-editor for reusability #76787

Icon block enhancements

• For example, the early prototype of the Icon Block had the following features, which we can consider as enhancements:
  • Flip icon (Vertical or Horizontal)
  • Rotate
  • Should we allow icons to have links?
  • Icon Block: Add flip and rotate transformation controls #77017

Customizable icon support for other blocks

Some icons render their own hard-coded SVG content or symbols. Make those icons selectable via the Icon API.

• Navigation block: Toggle button, Overlay Close button
  • Add more collapsed navigation icon options #61755
• Breadcrumbs: Separator (The text can be changed, but the icon cannot be used)
  • [WIP] Add icon support for Breadcrumbs separator in block editor #77059
• Navigation Overly Close block: Close icon
• Accordion Heading lock: Toggle icon (+ symbol)
  • Accordion Block open/close icon #73607
  • Accordion Block: Block uses + sign rather than SVG for icon #73214
• Details block: Browser default triangle symbol
  • Details Block: allow the option to choose from a set of icons #51019

Inline SVG icon (Inline format)

• At the moment I don't know how to implement this. Perhaps it will be based on "BITS". (ref)