Is there a feature or trick to automatically substitute or expand abbreviations to full phrases?
Yes, it's built into the system [&amp; can also share with any iOS devices you may have]

System Prefs > Keyboard > Text

There are a few there to start you off - if you don't want them, select &amp; hit the - button beneath.



Adding a new one is as simple as hitting the + button, type your trigger on the left [it wants something nice &amp; alphanumeric as a trigger, no punctuation]
The output can be pretty much anything you can imagine, including multi-line text, however, to get multi-line into it you need to copy/paste it from somewhere else, like TextEdit.  

The auto-generation of the shortcut in daily use is inter-dependant on your general spelling auto-correct settings, which will change its behaviour from only replacing on completion of the trigger then hitting Space, or offer to fill as soon as it thinks it has recognised what you are going to input.

I use it for anything from generating my signature, markup in Stack Exchange, to correcting some of my favourite typos that regular autocorrect doesn't seem to pick up.