I had the same problem as you.

My current understanding is that it's similar to Emacs, but in this case it uses Smalltalk instead of Elisp.

It's an IDE who's selling point is that you should extend while coding.

If my day job uses Python, for example, is it pragmatic to use Glamorous Toolkit? Yes, it has a few functions for editing code in some language .. but you get a lot more Python power from Intellij or Pycharm. I don't use Smalltalk but if I were, I would consider it, alongside Pharo or instead of Pharo.