This looks great! It would be good to add the units to the number as well though, it could be confusing working at different scales than this.

Hi Pablo, thats great. As the visualization seems placed at the meshes frontfacing boundingbox side rather than the current mouse position. Is it possible that you also enable this visualization while dragging the slider in the toolsettings remesh popup at the top of the viewport? I think it's as helpful if its contolled from there.

And even if it's slightly offtopic I'd find it very useful to have it the same way for radius and strength previews placed at the boundingbox side if brush radius and strength is setup from within the toolsettings.

On architecture side I think it is better to implement this as a gizmo as that will make it usable in other areas of blender.
I also added the UX team as reviewer to comment on the design and usability.

I also would like to mention that right now this is a workaround for an important bug in sculpt mode. When editing the voxel size directly in the mesh property Blender is constantly rebuilding the PBVH as you drag to tweak the value. That makes impossible to tweak the value in high poly meshes as the rebuild usually takes about 3 seconds. When you use this operator that does not happen.

Think this is an awesome feature - a very nice way to visualize what the operator does. I agree with Jeroen though, this should be implemented using gizmos.

@Jeroen Bakker (jbakker) @Julian Eisel (Severin) Is there any other functionality in Blender similar to this that uses gizmos to use as a reference for implementation? The most similar thing I found are the brush radius controls like WM_OT_radial_control and they are implemented the same way as this, they just let you choose a data path for the property to control (I can easily add that to this patch, but I don't think that makes much sense now).

@Jeroen Bakker (jbakker) One of the main advantages of this operator is its input curve compared to regular UI widget. The relation between the voxel size and the final mesh resolution is cubic, so the operator has more precise control automatically the higher the voxel size is to prevent you for jumping to a unmanageable mesh resolution when working with high poly meshes. The relation between the input and the voxel size does not feel consistent, but the relation between input and final mesh resolution is.
Also, I made the grid disappear when reaching small voxel size because and that point it adds to much noise to the widget and it does not produce any relevant visual information (it looks like a solid white plane). Most users now are used to memorized a set of voxel size values which produced a desired mesh resolution, that is why the number is there.

Would it be an idea to fade out the grid when the number is tiny. Not rendering it may feel like a bug and users will report it.

so.. now what is the shortcut to repeat the last action?