Element Tracker
The element tracker is a global UI on the screen that lets you change the currently active elements.
By default, the UI shows up horizontally at the top of the screen.

However, it’s also possible to show a vertical version of the tracker, by adjusting the respective option in the Options Menu. After reloading the game, the tracker shows vertically on the right of the screen.

The interface can be dragged to other places on the screen as well.
When an element is inert, its icon is greyed out. Left-clicking an inert element will make it strong and the icon will become fully colored. Left-clicking a strong or waning element will make it inert and the icon will return to its greyed out state. Right-clicked an element will set it to waning and half its icon will be colored.