Is a Sorcerer’s Flexible Casting visible?

Is there any RAW regarding what it looks like when a sorcerer is burning a spell slot into sorcery points? Is there any way to detect it? I’m thinking about a sorcerer in a social situation who uses subtle spell a lot to cast sneakily, and runs out of sorcery points and needs to make more while still being observed. Can they create more spell points without alerting the observers to the fact that they’re doing something magical?