Abbreviations Extractor add-on for Google Docs revolutionizes your experience by saving your time to extract the abbreviations and place them as a list in your prefrred location in Google Docs. 

Limitations: Free version lets you to extract only 10 abbrevaitions.

Disclaimer: This add-on uses a string matching library and Hence the efficiency cannot be compared to that of a Artificial Intelligence enabled tool. 
Further in some cases it is required for manual cleaning of some of the extracted phrases.