Open source assistive on-screen keyboard that runs on Windows
...Completely free, open source and compatible with low cost eye-tracking devices, it is a great alternative to often expensive and complicated AAC (alternative and augmentative communication) products. It can also be used as an alternative to a physical keyboard or mouse.
OptiKey runs on Windows and works right out of the box once an eye-tracking device is installed. Without an eye-tracking device however it can still be used with a mouse or webcam.
Unicode On-Screen Keyboard: insert text snippets into any Windows app
...The snippet can also be copied to clipboard.
It's basically a virtual keyboard with ability to set any amount of characters in one button.
Uosk comes with some preset keyboard: Arabic, box drawing, Devanagari, emoji, Greek, Hebrew, Hiragana, IPA, Katakana, Russian and Windows-1252.