You need to build the nCine from master as a static library and with the docking ImGui branch by using the following CMake options: -D NCINE_DYNAMIC_LIBRARY=OFF -D IMGUI_VERSION_TAG=docking.
Have a look at how GitHub actions build the artifacts by studying the workflow scripts: https://github.com/SpookyGhost2D/SpookyGhost/tree/master/.github/workflows
Let me know if you still have problems and join our Discord server for more help. ;)