Wagtail wish list: Copied Wagtail draft page should use new page title in the menu

[dorothyyeager]

Summary

What we are after:
Reported by Isaac B. in Info, but this has affected content team at various times too:
I’m preparing a new page for our 2021 Denver Regional Conference. The layout and most of the text will be the exact same as our 2020 San Antonio Conference page, so I copied that page. When copying, I gave it a new title, slug, description, etc. And it looks good in the draft. But on the Wagtail dashboard (screenshot below), it continues to say the name of the old page, even though the information within is updated.

What it looks like in Wagtail. Until the page is published, the name change doesn't take in the Wagtail interface as shown above. (That's really confusing.)

Technical considerations

Menu title was custom added by 18F - we could reference old PRs to see how it was done.
#1149 (comment)
#1200

Completion criteria

• Copied pages in draft status have their new menu title shown in the Wagtail directory display. These pages shouldn't need to be published to show the change.