Hi & welcome! Summertime seems to be the best time, but have done it when bored during the winter too. With a plant like yours, with multiple stems, you could cut one now, another when that has taken root, then another, so it never looks like it just got a drastic haircut. When you cut off the top part, the stump will grow one or more new tops. I've been doing them for decades, never used any hormone, just stick in a pot. The more length of stem I bury, the better the success seems to be. Just don't stick it so deep that the petioles (leaf-stems) are under.
