I checked sources and couldn’t find any implementation of glfwGetClipboardString and glfwSetClipboardString which use window pointer.
Do we really need window parameter in these functions?
Correct, the window pointer argument is no longer used on any platform, however there are still asserts that check whether the pointer is NULL. You can pass in NULL on release builds on Windows, macOS and X11. It may be safe on Wayland as well so I will look into deprecating the window pointer parameter and removing the asserts before 3.3 release.
It will likely be removed entirely for 4.0.