[aicayzer]

What changes for a person

• In the inspector's Relationships section, a group of links shows its first 20 rows and ends with a Show N More button. Choosing it shows the rest. The window remembers which groups are shown in full, for each item and group, until it closes. The group "Links in Content" works the same way.
• A link to an item in Recently Deleted carries a small Deleted label (trash symbol, secondary caption, in the style of the existing "Item not found" label). It still opens, in Recently Deleted, where the page is read-only with its Recover banner.
• A link to an item the library does not hold used to show a blank row. It now reads Item not found, opens nothing, and can still be removed from its menu.
• A group's links are now ordered by title (then ID) for outgoing links too, so the same 20 come first each time.

What I chose

• Opening a deleted item follows what MAPP already does for one: Recently Deleted is the only place that lists it. Browser.reveal (palette, table parent link, page links) had sent a deleted item to All Items, which does not list it; it now goes to Recently Deleted as well.
• A group of 21 shows 20 rows and "Show 1 More", as briefed.
• Expanding is one step (all remaining rows), and expanding again changes nothing.

Tested

Unit plan, run once locally: all pass. New LinkListTests cover groups of 0, 1, 20, 21 and 500 (rows, hidden count), expanding once and twice, state per item and group, a binned link and its recovery, a missing link, adding and removing links live, and where a deleted item opens.

Not seen

No window was opened, so the look of the button and label, hover fill, and spacing are unchecked on screen. Two String Catalog keys were appended by hand ("Deleted", "Show %lld More").