I don't know about command line, as I never used it, but Plesk up to 8.6 I could set exclude folder in GUI backup program and exclude as wildcard, so I could exclude all my big folders, backup folder etc.
Not as the GUI program (separate from web plesk) is gone, I have no option to exclude files or folders (not domains!).
Any way to get this back so I can upgrade my servers to 9.2?