happy to see that we habe both the same toughts 
Basically I want to avoid to write the same text twice
that we would be what? number of pharagraph in the note, count characteres etc. ?
Wouldn't it be save to mark the text and put in lable it. Allow to give it specific name or use guid, e.g.
[extractor] ...text ... [/extractor=my first reused pharagraph]
could be convenient but not sure, as you don't know where else the text is used. It may does not fit anymore at other places.
If you combine it with back-links you have chance to know where the text used.
btw, I'm trying to figure out how it could be used with Plugin: Note Link System. Would be greate the pharagraphs get IDs to use them by the other plugin too.
Could be that the featuer is currently failing: Plugin: Note Link System - #138 by PackElend
My current focus is to build an extend Glossary:
Any suggestions on what plugins could be created? - #240 by PackElend + How to use Joplin to create a Wiki including Glossary