If you mean the Unicode glyphs listed at https://en.m.wikipedia.org/wiki/Block_Elements they are supported - you just need a display driver that can render them. For example, `twin --hw=xft` (it's the default) or `twin --hw=X11`, both with a font that contains them
Xe means the Unicode block that is actually named "Symbols For Legacy Computing". It's not in the BMP. Some bloke named Bruce was doing TUI windows with scrollbars and sizer/menu boxes some years before TurboVision and code page 437. (-:
Indeed I meant these: https://en.wikipedia.org/wiki/Symbols_for_Legacy_Computing
I use them in some tiny hobby projects like these:
https://github.com/panzi/progress-pride-bar
https://github.com/panzi/bad-apple-terminal
https://github.com/panzi/js-unicode-bar-chart
https://github.com/panzi/js-unicode-plot
https://github.com/panzi/js-unicode-progress-bar
https://github.com/panzi/python-term-flags
Reading the flags one: Unscii has font coverage, if you want to try that out on the emulators whose fonts were problems.
* https://news.ycombinator.com/item?id=43812026