Checker
Checker is a component (like trigger) of many Mappet features which allows you to program whether something should happen or not, i.e. a feature that lets you setup a condition under which it will work/be enabled. Checker is a hybrid that allows using either expressions or condition editor.
The toggle button that looks like 🔃 allows to toggle between an expression that can be typed in (or Edited in fullscreen... by right clicking the text field):
and a button that allows to open the condition editor modal:
