What?
The small check mark at the bottom right corner of the Class Properties Pane is to be used to confirm any editing you do for the properties of a class

Watch-out!
One common slip-up is when someone edits properties of the class; but then forgets to click on this button. Internally, the model would still be having the old values – it does not know that you had changed it! This can result in wrong outputs in ARDELA and the 3D view, exports etc