How to Cancel Concentration
On controller it was just holding Triangle down (don’t remember if you need to be in radial mode, hovering over said spell or not).
Open the radial menu for the character that is concentrating so hard and navigate to that spell. When hovering over it, you’ll see options in the lower right corner of screen. It shows to hold ( Y ) down to cancel concentration.
I never noticed that before. Other Deck users might appreciate this tip, if they can’t read their own screens, like me!