For instance I want to install neovim-0.11.0-1.fc42 which is currently labeled testing > stable on the top right.
It seems like its a matter of days until the nvim 0.11.0 Fedora package is ready, but I would like to know in case I want to want to install other packages, especially if it takes over a week for new versions of nvim.
dnf install --enable-repo=updates-testing neovim
This enables updates-testing for this dnf invocation only. In particular, it will look for neovim as well as any dependencies in updatest-testing (in addition to any other enabled repos).