Is shortening the standing in supererogatory prayers while prolonging the bowing, prostration, and the two moderate pauses considered in accordance with the Sunnah, or is it contrary to what is better? And what is preferable in that regard?

If the intention is to prolong bowing (ruku'), prostration (sujud), and the standing postures between them more than the standing (qiyam) itself, then this is contrary to the Sunnah. The Sunnah is for the standing to be longer than all other pillars. If the question is about the preference between prolonged standing and frequent bowing and prostration, the opinions of jurists have varied. Some say that prolonged standing is absolutely better, others say they are equal, and some say that prolonged standing at night is better, while shortening it during the day with frequent bowing and prostration is better. The Sunnah in prayer generally, whether at night or during the day, is for the duration of standing, bowing, and prostration to be close to each other. The true matter is that the best in prayer is for it to be moderate, so if one prolongs the standing, they should also prolong the bowing and prostration.