What's even better:
these are desktop apps ported to the Kindle, not dumbed down versions, as it's often the case for mobile devices. It's really hard to find good quality text editors for Android tablets.
They have a small learning curve - these are not
Word clones, and not
Notepad either - but once you understand how to use them, they become extremely capable.
One more recommendation: Use
Syncthing to set up a sync folder between the Kindle and your computer, it will automatically synchronize all your documents when on the same network.