Double/curly underlining?

[vefatica]

I've seen references to Double/curly underlining (and others). Are the control sequences documented anywhere?

[lhecker]

I believe kitty introduced these sequences; they're documented here: https://sw.kovidgoyal.net/kitty/underlines/
This has a few examples for color as well: microsoft/vscode#158827

[vefatica]

Thanks, Leonard. They work in WT. Aren't they mentioned any where in this forum or in any WT docs? How is one to know about them?