Smooth icon, left bar 2.8. Doesn´t work like 2.7 Iam getting back to blender after some years (I was just modelling ocasionally for simple figures, getting back again).

I used to use "smooth vertex" on 2.7 to make cleaner and flatter faces on the mesh as I was modelling, It helped to maintain from the beginning a nice model for 3d print, or clean faces in any ways. The "smoothed" vertex located into a better position if required. 

Now I can see the "smooth" icon on the left but I can´t select it. :( 

What am I missing?
Select the wanted vertices.

Select the smooth button on the left.

Then left click on the 3D view and drag the mouse left or right.

Additionally, the operator panel allows to set the smooth value manually.



Note: a long click on the smooth icon makes appear another operator which is 'randomize vertices'.