Note: If you are just getting started with Articulate Storyline, note that you can allow any object (including shapes, images, and text) to be dragged by using the trigger ‘when the object is dragged over’ from the trigger wizard.
After a little thinking, I came up with another solution; and this is what I did:
2. Placed the rectangle over the brush; therefore, the brush was still visible, but no longer clickable. In other words, I had disabled the drag functionality of the brush.
4. Created another trigger to hide the rectangle once the state of the brush is changed.
Thus, an invisible shape was all I needed to temporarily disable the drag functionality in Articulate Storyline.