Version 10.12 of Mac OS X (aka Sierra) provides support for opening
documents in a tab instead of a separate window.
As a consequence, Alpha now supports window tabs if it is running on Mac OS X
10.12 or greater.
You may specify, at the system level, when documents open in a tab:
choose Apple menu ↣ System Preferences, then select Dock.
click the Prefer tabs when opening documents pop-up menu,
then choose an option:
Always
In Full Screen Only
Manually
By default, documents open in tabs only when an application is full screen.
In order to interact with window tabs, there is a Tabs
menu (which is a submenu of the Open Windows menu),
with the following items:
Select Previous Tab (⌃⌥⌘-Left)
Select Next Tab (⌃⌥⌘-Right)
Move Tab To New Window (⌃⌥⌘-Up)
Merge All Windows (⌃⌥⌘-Down)
On version 10.13 of Mac OS X, there is an additional menu item:
Toggle Tab Overview
Note that if you are running Alpha on OS X 10.9, 10.10 or 10.11, the Tabs
menu will not appear.
That's all there is to it. Enjoy !