https://github.com/BalazsJako/ImGuiColorTextEdit
'Rich' text editing might hit limitations with Dear ImGui's text rendering (e.g. not sure if things like italics, bold or strikethrough are supported out of the box).
Font handling is based on stb_truetype.h, but can be replaced with FreeType:
https://github.com/ocornut/imgui/blob/master/misc/freetype/R...
In any case, versatile text rendering is certainly not the design focus of Dear ImGui (AFAIK there's also no support for RTL layout), instead it is mainly targeted at quickly creating specialized UI tools (especially inhouse tooling for game development), less at creating end-user applications.
There's plenty of UI frameworks to create "end-user applications", but hardly any that fill the specific niche served by Dear ImGui.
https://floooh.github.io/sokol-html5/sgl-microui-sapp.html
https://floooh.github.io/sokol-html5/nuklear-sapp.html
IMHO Nuklear goes a bit too much into the 'immediate mode design purity' direction which makes it a bit less convenient to use than Dear ImGui.
Microui is indeed a very minimal UI, but might be useful for just adding a small controller UI (similar to dat.gui in the JS world).
Sorry about the confusion.
E.g. in microui 1.x defining a window worked like this:
static mu_Container window;
if (mu_begin_window(ctx, &window, "Style Editor")) { ... }
...in microui 2.x it's no longer necessary to store the window state on the user side: if (mu_begin_window(ctx, "Style Editor", mu_rect(350, 250, 300, 240))) { ... }