Reading this hint gave me an idea for a new feature for my Safari extension, Tabkeys. Tabkeys is an extension that lets you assign custom hotkeys to tab actions, such as opening a new tab or closing the current one.

The new feature is an option that determines what happens when you close the last tab of a Safari window by hotkey. If the option is enabled, Tabkeys will replace the tab with an empty one instead of allowing Safari to close the window. The option is disabled by default, so if you want this behavior, be sure to set the option on the extension's General settings page.

The feature only applies when using ⌘W or a custom hotkey to close the last tab. It has no effect if you click the window's Close button or use the Close Window menu command.

That's genius. I've now installed Tabkeys and can confirm it does automatically what my hint did manually. Nice work, canisbos!