Introduction and Demonstration of Magit in Emacs.
Context: This is going to be used as a caption. Magit is a software that runs inside the text editor called Emacs. Should I use "inside" instead of "in"?
Introduction and Demonstration of Magit inside Emacs.
Any suggestion is appreciated.
Right away I see a problem. It seems to be saying "introduction of Magit", but "introduction" does not take "of". You say it's a caption. That normally means a descriptive phrase under a graphic, but an introduction to a piece of software and a demonstration of it sounds like it would be an awfully big graphic, we use sentence capitalization for captions, and there is normally no period at the end. The upshot is that I am not sure what we're talking about.
To make your caption grammatical, if caption it be, you would have to accommodate the correct prepositions for the two nouns, maybe "Introduction to Magit and demonstration of it within Emacs". You can't just toss in the right preposition for "introduction" because if it was "Introduction to and demonstration of Magit within Emacs", that would mean that the introduction was within Emacs, which is not what you mean.
I would use "within".