Yes, there are things like https://github.com/ocornut/imgui, and some (especially open source) applications try and muddle a long with Qt or GTK, but many (most?) serious professional or power user applications have built their own GUI frameworks or at least custom controls to deal with this.

Whatever route you take, as a dev it's painful, especially for someone who remembers adding a couple of libraries to a Delphi project back in the Office 2000s era and getting full docking, configurable toolbars, etc. with little to no work.

So the easy fallback (especially with the recent proliferation of libraries) is TUI and CLI applications with the layout/docking and tabs provided by the terminal emulator itself or one of tmux/zellij/etc.

I've been thinking on and off for a few years now about the idea of a "graphical terminal", sitting somewhere between a GUI toolkit and a terminal emulator and a full blown OS for building inter-composable apps and tools and components that could replace TUI based workflows/apps/layouts. I have a vision of every "pro" app just being a different curation and configuration of underlying components rather than actually separate software.