an example using tiddlywiki (content/edit mode on the left, preview on the right side)
provided that transclusions are more seamlessly integrated to the core text, the use cases can be very broad. In tiddywiki, I use multilevel transclusions for code snippets, rules for board games that share similar concepts, tracking things & to do lists : embed a task in a day,embed the day+task in week, embed the week in a month, then embed the same task in a project, etc… and it works beautifully since the transclusions are seamless.
there are no visual delimiters between normal text and tansclusions (a transclusion could be a single word embedded in a sentence).