How to update rule tile (brush) from Unity’s 2D grid tile map palette?

I have created a Palette in Unity and created a map using that rule
draw map

Now, I want to replace the current rule with another one, without having to draw everything once more. I tried to drag and drop the new rule on the same position in the palette, but the drawn map was not updated.

enter image description here

I am a little anxious about creating a (large) map unless I know of a way to update a brush without having to redraw everything.