"Why, oh why, oh why, oh why, don't people just use Unix?

dd if=input.txt of=output.txt conv=lcase"

I am an old UNIX 'Guru/wanker' from nearly 30 years ago.

Your example is useless for most of my needs. I want to (using visual feedback) highlight a small section of text, and manipulate it to
1) All upper case
2) All lower case
3) All in Word Capitalisation
4) Inversion of case
5) and there are many other 'Chindogu' style manipulations that one has occasional need to use, but on only small selected (visual is easiest/fastest) portions of text, not a whole file stream.