I have been using Trados for many years. My first works in Trados are from 2004.
When I worked with Trados 2007, I often used the function where you could save words under an abbreviation. The word then appeared when an F key was pressed. You removed this function when you launched Trados Studio 2009. You introduced the AutoText function instead.
However, the AutoText function is poorly adapted for technical texts. Since many technical words have the same introduction, e.g. motor-, a line of suggestions may appear when writing the first letters. There may be 20 suggestions or more. This is not helpful. Then it is often faster to print the word yourself.
In the old Trados version, you could decide for yourself what a long word should be shortened to. It was much more useful, especially in technical texts.
I hope with each new edition of Trados Studio that even the function where you can get used to the abbreviation of a long word, will come back. However, this has not yet happened.