You actually mean Manjaro Stable, extra is just the repo where pretty much all the external software is (and there is extra repo in each branch).
You should not force install only 1 package from other branches. It will create problems with dependencies.
In case you only need newer freecad on stable, the right approach is to use a containerized format like flatpak or appimage, which is supposed to have all dependencies. In that case, the official freecad site offers appimage.