I think currently the answer is that you can't.
The limited function is what you see with in/out and merging. But, as you recognize, that is only useful if you know that only certain sections of your sequence were changed.
In the Beta version, they are working on "Text Based Editing." There are 2 types of transcriptions - Source media, which will adjust to changes in the timeline and Static transcription (the current method) that are used to create captions. This may help.
The Beta just renumbered to 23.5 from 23.4, so I am hoping this makes it into the next major release.