OS X El Capitan: ABC Extended Keyboard Capabilities

Apple’s ABC Extended input source (called "US Extended" prior to MacOS 10.11) lets you type a vast number of accented and special Latin characters. A common standard reference for its shortcuts is at

https://sites.psu.edu/symbolcodes/mac/codemacext/

Unfortunately that reference is missing the following deadkey shortcuts which have been added at some point in recent years:

+Option-Shift period: Characters with hooks: Ɓ ɓ Ɗ ɗ Ɲ ɲ ñ Ƴƴ

+Option-Shift semicolon: A variety of phonetic symbols like ə ŋ ɣ ȝ

+Option-Shift g: Characters with circumflex below.

+Option-Shift f: Characters with tilde below.

A custom layout which adds Umlaut Below to ABC Extended is available here.

To see the full range of characters available with this keyboard, use Keyboard Viewer.