Right-click on a tab, choose 'Move Tab >' and then choose a named window. The tab disappears from its previous window, but does not appear in the chosen named window or any other window - it's gone.
After the tab disappears it is not shown in 'Recently Closed Tabs'. 'Reopen Last Closed Tab' does not reopen the lost tab. But its page is available in normal History.
However: moving a tab to an un-named window, or to a new window, does work as expected.
The moved tab should appear in the chosen named window.
0.99.132-beta
Sequoia (15)
