A smart text tagging system

Have you ever written a bunch of notes, stream of thought, ideas, tasks, memory joggers, diary log, how you did something, solution to problem etc etc so you can go back and find some information again if the need arises?
Trouble is it is very hard to find info again unless you remember a key word, and strangely you often dont as you used different words or abbreviated in your original notes for eg.
So - to better consolidate your notes - cut and paste your notes into a new subject related doc. Eg all car maintenance or related notes - cars.txt.
But I want to know what notes I copied from my original notes doc.
I want the process to be easy and quick.

Solution - a button bar floats over my doc with say 8 different color buttons.
I click on green button. Then I can highlight any text by click and hold mouse button to change text to that color. I keep going through the doc doing this for all text in the related subject. At the end of this process I hit a button to copy all this green text into a new doc in the same order as it was in the original doc. Options could also include delete the text from the original. I would repeat the process of tagging related texts with different colors. The colors allow me to see which text has been tagged and avoids me creating duplicates as conventional copy paste would do. Easy peasy.