What?

Closes #77071

Implements the editing-only portion of the extensible Site Editor sidebar navigation work by allowing existing navigation items to be edited directly from list view.

This PR:

• Adds an Edit link action to the sidebar item menu for core/navigation-link and core/navigation-submenu
• Reuses the existing navigation LinkUI so existing items can be edited in a popover without switching to the canvas
• Anchors the popover to the active sidebar row and applies sidebar-appropriate spacing/positioning
• Preserves the current cleanup behavior for newly inserted empty placeholder links
• Avoids removing existing navigation items when their edit popover is closed

See also: #77069, #75921, #76428, #77072

Why?

Today, users can reorder and remove items from the extensible Site Editor sidebar, but they cannot edit an existing navigation link from that surface. To update a link label or destination, they currently need to move back into the canvas.

That gap is tracked in #77071 and is part of the broader work in #77069. A related earlier PR, #76428, explored the same problem, but review feedback there asked for the editing behavior to stay separate from broader suggestionsQuery / search changes, which are better handled independently in #77072.

This PR keeps the scope narrow and focused on the in-place editing experience.

How?

The implementation threads sidebar edit state through the navigation menu list view and reuses the existing NavigationLinkUI for existing blocks, not just newly inserted ones.

More specifically, it:

• Stores the currently edited block in the sidebar navigation screen
• Adds an Edit link menu item in the sidebar row actions for navigation links and submenus
• Updates NavigationLinkUI so it can operate on either:
  • a newly inserted navigation item, or
  • an existing navigation item selected from the sidebar menu
• Keeps the existing cleanup behavior for auto-inserted empty links
• Prevents accidental removal of existing links when the popover closes
• Anchors the existing-item edit popover to the active list-view row and applies desktop sidebar spacing so the popover opens in the expected position

The PR intentionally remains focused on editing behavior and does not broaden link suggestion/search behavior beyond this scope.

Testing Instructions

1. Start Gutenberg locally.
2. Run npm run wp-env status.
3. If the environment is not running, run npm run wp-env start.
4. Open the Site Editor.
5. Open the Navigation screen and choose a menu.
6. Open the three-dot menu for an existing Navigation Link item.
7. Confirm an Edit link option appears.
8. Click Edit link.
9. Confirm the link popover opens from the sidebar list view without switching to the canvas.
10. Confirm the popover is positioned with normal spacing from the sidebar, rather than being flush against the left edge of the screen.
11. Change the label and/or destination.
12. Confirm the item updates correctly.
13. Reopen the three-dot menu for an existing Navigation Submenu item.
14. Click Edit link.
15. Confirm the submenu link popover also opens correctly from list view.
16. Close the popover for an existing item without making changes.
17. Confirm the existing item is not removed.
18. Add a new blank navigation link from the sidebar flow.
19. Close its popover without entering a URL.
20. Confirm the empty inserted block is still cleaned up and removed.

Testing Instructions for Keyboard

1. Open the Site Editor and navigate to the Navigation screen using the keyboard only.
2. Move focus to an existing navigation item in the sidebar list view.
3. Tab to the item actions button and press Enter or Space.
4. Use the arrow keys to move to Edit link.
5. Press Enter.
6. Confirm focus moves into the link editing popover.
7. Use the keyboard to update the link label and/or destination.
8. Confirm the item updates without requiring canvas interaction.
9. Reopen the popover and press Esc.
10. Confirm the popover closes and focus returns to the sidebar flow in a sensible place.
11. Repeat for a Navigation Submenu item.
12. Add a new blank navigation link from the sidebar and close it with the keyboard.
13. Confirm the empty placeholder link is removed as expected.

Screenshots or screencast

• Before: existing navigation items in the sidebar have no in-place edit action

• After: Edit link opens an in-place popover from list view with correct spacing and no canvas switch

Before	After
Existing navigation items cannot be edited directly from the extensible sidebar list view.	Existing navigation items can be edited from the extensible sidebar list view via an anchored popover.

Use of AI Tools

This pull request involved an AI-assisted review.

• Codex and Claude to verify the patch & any possible improvements.

All generated output was manually reviewed, validated, and adjusted before submission.