I'm having trouble finding a satisfying answer to the following question:
To describe perfectly a Keplerian orbit, one needs 6 orbital parameters: $a$ the semi-major axis, $e$ the eccentricity, $i$ the inclination, $\omega$ the argument of periapsis, $\Omega$ the longitude of ascending node and $\nu$ the true anomaly.
We sometimes see corner plots in scientific papers discussing orbital mechanics and orbital elements predictions where $\omega$ and $\Omega$ are not represented separately but jointly as $\Omega-\omega$ and $\Omega+\omega$.
Is there a specific reason for such a representation? I can't figure out what $\Omega-\omega$ and $\Omega+\omega$ represent in terms of angular quantities.
If one of you knows, I'd be glad to hear an explanation.