How to Prune orchid cactus 'Celestial Snow'?
No pruning required

orchid cactus 'Celestial Snow' · Epiphyllum 'Celestial Snow'
In areas where temperatures drop below 10ºC, grow in epiphytic cactus compost in bright filtered light as houseplants or in a warm greenhouse with moderate to high humidity, and a minimum temperature of 10ºC for most of the year but 15ºC in the growing season; from mid-spring to late summer water freely and apply a high-potash fertilizer every 2 weeks as flower buds form, while in winter keep just moist. In warmer climates, grow in fertile, sharply drained soil in light dappled or partial shade. For more advice, see Epiphyllum cultivation
No pruning required