How do I switch my active item and held item (runes, cards etc.)?

[Grunt]

So I have 2 for both of them but I don't know how to switch and can't find the key bindings anywhere.

[patrol]

Ctrl

[RZA]

I think you press CTRL

[Lan]

CTRL to switch, right trigger for controller, or hold them to drop trinket and card/rune.

[The Renderer]

Or look into your controls for the "drop" button. Short press to switch items, long press for dropping. Key binds are in options -> controls -> whatever you use.